text:
Talk:Diameter

other guy
I came to this page to find out about the diameter sign. I believe it's ⌀ (Unicode 2300, looks kind of like ø), as opposed to ∅ (empty set, Unicode 2205, looks kind of like Ø). Maybe one of you math types could mention the diameter sign in the article? -- user:Nate Silva

I'm one of those "math types" and I've never heard of this symbol? In what contexts have you seen it? Michael Hardy 22:27, 11 May 2004 (UTC)

I'm another "math type" and I've never seen or heard of a a"diameter sign" before. Math textbooks don't use it. --Dbenbenn 06:04, 11 Dec 2004 (UTC)

Diameter sign is used mostly on technical drawings (mechanical) to indicate that shape is round, not square. --andrejj 06:56, 11 Dec 2004 (UTC)

I like the way the symbol is explained here, and the mention of the Scandinavian letter as a replacement. Could someone maybe add an explanation that this is NOT exactly the same as the Greek letter "phi"? It's mentioned here:

http://goldennumber.net/phisymbol.htm

and in Wikipedia:

http://en.wikipedia.org/wiki/Phi#Use_as_a_symbol

Thanks. Marzolian (not logged in)208.185.201.194 (talk) 00:29, 31 March 2011 (UTC)

 * I've had some courses in engineering a while ago and have always heard the diameter symbol called "phi". Cosidering that the "source" above never even mentions a "diameter symbol", i'm going to put cns on the statements here and at Phi. -- Jokes Free4Me (talk) 04:10, 11 February 2012 (UTC)

triple a systems
Hi,

I am missing a link to the Diameter Computer Protocol (AAA-System). thanks

Definition of a diameter
I have heard that the formal definition of the diameter (for an arbitary closed curve) is that:
 * A diameter is the locus of mid-points of a set of parallel chords intersecting the curve.

Is it true? If yes, then it should be mentioned in the article. — Ambuj Saxena (talk) 18:04, 22 July 2006 (UTC) s

 * Chords don't intersect the curve - so what do you mean here? But a definition in one of my maths textbooks was a straight line that is the locus of midpoints of parallel chords.  The curve doesn't have to be closed - so for example, parabolas have diameters (parallel to the axis), as do hyperbolas (IIRC, intersecting the centre).  By this definition, polygons have a finite set of diameters, e.g. the diameters of a parallelogram are the diagonals and the line segments connecting the midpoints of opposite sides. — Smjg (talk) 23:11, 14 January 2014 (UTC)

Outside of mathematics, "diameter" denotes, not a line, but the greatest distance spanned, usually by a concrete object such as a lesion or a rock. I tried to communicate this following the sentence about the hull in the Generalizations section. Hopefully, there is a clearer way to express this for non-mathematicians. Myron (talk) 10:03, 17 April 2015 (UTC)

Reuleaux polygon
I'm not sure what the definition of diameter of a Reuleaux polygon is but surely it should be mentioned? If it is just the line that goes through the centre then it shouldn't say "the diameter of a circle" but "the diameter of a Reuleaux polygon, and trivially, the circle" or some such, to avoid loss of generality? Triangl 22:54, 16 January 2007 (UTC)

Only in Word
Alt-8960 doesn't work for me Windows-wide. Only gives diameter sign in Word. Not even in Excel. (WXP SP3, Office 2007) —Preceding unsigned comment added by 94.248.136.34 (talk) 00:21, 3 February 2010 (UTC) Windows-wide ALT code for ø is ALT + 0248. (W7 SP1) -- JoelAlejandro

I have always used ALT + 0216 = Ø Zarboki (talk) 00:38, 27 March 2012 (UTC)
 * ALT + 0216 is actually a Nordic vowel that looks similar (but not identical) to the diameter symbol. It's probably "good enough" for most people, but it's not quite accurate. Fieari (talk) 14:38, 6 January 2014 (UTC)

According to the W3C, the preferred code for Diameter is actually & #8709;. I'm not sure how well this matches up with Unicode. I was unable to get windows to properly type the diameter symbol using any ALT + #### codes. Fieari (talk) 14:38, 6 January 2014 (UTC)

 * &#8709; gives the Unicode character U+2205, which is an empty set sign. Whatever the W3C says, using this instead of a diameter sign is no better than using that Nordic vowel as a diameter sign. --Zundark (talk) 18:44, 6 January 2014 (UTC)

Revert
I don't know why the perfectly good description of the symbol (which was the bast thing about the article) was removed. I found it Cached in Google and I have put it back. --24.80.177.199 —Preceding unsigned comment added by 24.80.177.199 (talk • contribs) 22:44, 1 February 2007
 * See Help:Reverting for the correct way to restore an earlier version. --Zundark 13:11, 2 February 2007 (UTC)

In fact, diameter is a very contraversial matter to be treated with utmost respect. - —Preceding unsigned comment added by Aes-Sedai (talk • contribs) 10:11 (2 edits), 15 June 2007

Explanation
I think i understand the language in the "Diameter symbol" section
 * The symbol or variable for diameter ...

namely that the same character has two purposes, standing for the word diameter, as in
 * 2"⌀ pipe

and also serving as a variable, as in
 * ⌀ = 2"

But it would be better for someone accustomed to regularly using it, as symbol, variable, or (preferably) both, to clean up that paragraph. --Jerzy•t 06:14, 29 February 2008 (UTC)

Diameter symbol definitely in Unicode as of 2020
Just in case modern readers are misled by this 12 year old discussion, I confirm that the symbol is definitely in Unicode. See. It is the Miscellaneous Technical block. --John Maynard Friedman (talk) 17:11, 5 April 2020 (UTC)

 * In fact, it has been in Unicode since 1993, if not earlier. (The discussion about using other symbols in place of it was because U+2300 often wasn't easy to use, due to lack of support by fonts and/or software.) --Zundark (talk) 20:28, 5 April 2020 (UTC)
 * That doesn't surprise me: what surprised me was that it was an issue in 2008 when I just took if for granted that the basic plane had been settled long before then and concluded that it had to be me who was wrong! --John Maynard Friedman (talk) 20:43, 5 April 2020 (UTC)

Spelling
The Metre article has the British spelling, so why isn't this called diametre? It seems stupid to change into American spelling just because a prefix has been added. --The monkeyhate 17:50, 11 August 2007 (UTC)

 * The American spelling is also the British spelling. There's no such word as diametre. --Zundark 18:04, 11 August 2007 (UTC)

 * Is that so? I believe you, but it's rather illogical. --The monkeyhate 19:55, 12 August 2007 (UTC)

 * Where on Earth did you get the idea that British spelling is logical? You must be from Sweden or something (and hate monkeys). Justice for All (talk) 00:06, 24 October 2008 (UTC)

Measuring instruments use "meter" ie, multimeter, the unit of measure is "metre". Not complicated ;-) Zarboki (talk) 00:36, 27 March 2012 (UTC)

the diameter of the circle
24.17.137.175 (talk) 02:56, 29 March 2009 (UTC)Kiera24.17.137.175 (talk) 02:56, 29 March 2009 (UTC) == Headline text

what is diameter? the essence of a circle that the endpoint outlines.

Symbol is box
How come the symbol is a box for me? I'm using UTF-8. — M C  10  |  Sign here!  03:24, 21 July 2009 (UTC)
 * Probably because your browser doesn't have access to a font with that symbol in it? See Help:Special characters. —David Eppstein (talk) 03:56, 21 July 2009 (UTC)

Image confusing?
For someone unfamiliar with the meaning, might the image suggest that the diameter only extends to the centre? So I wonder if we should show the diameter line in red (or do something to indicate that more strongly indicates the extent.--A bit iffy (talk) 10:32, 21 August 2011 (UTC)

 * See current image on main page. John W. Nicholson (talk) 06:19, 7 September 2013 (UTC)

Nuts, bolts, screws
Should not there be a section with different objects like nuts, bolts, and screws which standard measurements are in diameters. — Preceding unsigned comment added by Reddwarf2956 (talk • contribs) 23:36, 24 August 2012 (UTC) All nuts,bolts,and screws should have a diameter.

 * See Screw thread. A the moment, this article ignores real-world uses where different types of diameter are often needed and used. In the case of the transverse section of a screw - across the threaded part itself - this article would have you convinced that only the major diameter is considered. However, the pitch diameter is quite an important consideration to ensure proper fitting of bolts and screws as well as gears. Tomásdearg92 (talk) 12:34, 16 February 2014 (UTC)

⌀ symbol used in engineering drawings and camera lenses
I ended up here as I found an SLR camera lens with "55⌀" on the front rim.

The Ø section says "The diameter symbol is used extensively in engineering drawings, and it is also seen anywhere that abbreviating "diameter" is useful, such as on camera lenses." Unfortunately, no citations were given though I suspect once a WP:RS is tracked down we can add this to the Diameter article. --Marc Kupper|talk 01:53, 9 March 2016 (UTC)
 * More specifically for camera lenses that take front filters it is the filter diameter (in millimeters). —David Eppstein (talk) 03:11, 9 March 2016 (UTC)

Definition of "width"

Currently the lead says without a citation

 * For a convex shape in the plane, the diameter is defined to be the largest distance that can be formed between two opposite parallel lines tangent to its boundary, and the width is defined to be the smallest such distance.  [my bolding]

But the lead of our article Mean width gives the definition shown in this diagram—the width is direction-dependent and varies for a given figure, rather than being a minimum for that figure. And that definition fits in with the notion of a curve of constant width—the word "constant" implies that for other curves, the width is not constant over the curve but rather varies over the curve.

Unless I see an objection, I'm going to change this accordingly in this article. Loraof (talk) 20:12, 30 April 2017 (UTC)
 * All three definitions — direction-dependent width, mean width, and minimum width, are in use. Please do not change it in a way that makes "width" refer only to the direction-dependent version, because it is not true that it is only used that way. The specific source used for this claim doesn't appear to discuss this issue directly, but is most immediately applicable to minimum width. —David Eppstein (talk) 20:37, 30 April 2017 (UTC)

No Pi?
No mention of pi? Circumference is mentioned only in the diagram. Feldercarb (talk) 22:16, 29 May 2019 (UTC)

Navbox punctuation and other typographic symbols
My addition of template:navbox punctuation was reverted per WP:BRD, so here is my justification for including it.

First, the name is shorthand for the long title "Punctuation and other typographic symbols". The diameter symbol is an example of the latter and this why the navbox at the end of the article is appropriate.

(I probably jumped the gun because Template:Navbox punctuation/sandbox hasn't gone live yet but when it does, it will be rather more clear what is going on. I'm happy to discuss this BRD now but recognise that it won't be appropriate to push for inclusion until after the new navbox is released.) --John Maynard Friedman (talk) 17:03, 5 April 2020 (UTC)
 * I have added the punctuation and typography navbox again, at the end of the article. It contains the diameter symbol and many others: this helps readers find this article and helps readers of this article to find related articles. To facilitate discussion, I have initially set the state to 'collapsed', to facilitate review and discussion. --John Maynard Friedman (talk) 10:35, 20 April 2020 (UTC)
 * As there has been no comment either way, I have removed the 'collapsed' setting. --John Maynard Friedman (talk) 16:24, 1 May 2020 (UTC)

"Diamètre" listed at Redirects for discussion
An editor has identified a potential problem with the redirect Diamètre and has thus listed it for discussion. This discussion will occur at Redirects for discussion/Log/2022 February 14 until a consensus is reached, and readers of this page are welcome to contribute to the discussion. User:1234qwer1234qwer4 (talk) 06:06, 14 February 2022 (UTC)

Not manual
Per WP:NOTMANUAL, we don't generally include a list of instructions on how to type a character. Before I attempted to clean it up, the section on encodings had this level of detail: "The symbol has a Unicode code point at, in the Miscellaneous Technical set. On an Apple Macintosh, the diameter symbol can be entered via the character palette (this is opened by pressing Opt in most applications), where it can be found in the Technical Symbols category. In Unix/Linux/ChromeOS systems, it is generated using Ctrl 2. It can be obtained in Unix-like operating systems using a Compose key by pressing, in sequence, Compose. In Windows, it can be entered in most programs with Alt code 8960.

The character will sometimes not display correctly, however, since many fonts do not include it. In many situations, the Nordic letter ø at Unicode is an acceptable substitute. It can be entered on a Macintosh by pressing Opt (the letter o, not the number 0). In Unix/Linux/ChromeOS systems, it is generated using Ctrl F or Compose. AutoCAD uses available as a shortcut string %%c.

In Microsoft Word, the diameter symbol can be acquired by typing 2 and then pressing Alt.

In LaTeX, the diameter symbol can be obtained with the command  from the 'wasysym' package."

As I understand it, there are two, possibly three ways to encode the character: U+2300 in Unicode, the command \diameter in LaTeX and (arguably), &&C in AutoCad.

AFAICS, going into the detail of how to implement those encodings in a document falls foul of WP:NOTHOWTO. We should just refer readers to relevant articles such as Unicode input and LaTeX. So I'm at a loss to understand why user:Spitzak believes that the compose key material should be restored and user:David Eppstein believes the same about the information on how to write LaTeX. Since I have the greatest respect for both of these editors, I have to wonder it is that I am missing. What is unique about this case? and if these two are to be reinstated, then surely the Windows and MacOS instructions should be reinstated too? 𝕁𝕄𝔽 (talk) 22:55, 4 May 2024 (UTC)
 * As far as I can tell, your reading of notmanual and nothowto is bogus. Encyclopedia articles should not read like tutorials, but this does not mean we are forbidden from explaining the how of an encyclopedic topic. We should not go step-by-step (first find the key marked with a cloverleaf symbol, then hold down that key and the Q key), but a concise explanation of how certain characters are encoded on the keyboards of commonly used systems, with sources, is perfectly appropriate. Or do you think that articles detailing how certain processes happen are somehow forbidden from Wikipedia? For instance, do you think we should not have an article long division because it is about how to calculate divisions and that word "how" makes it forbidden? Use your brain, think about what the guidelines mean, don't just blindly follow rules because you read them somewhere. If a rule comes across as an arbitrary prohibition rather than something that is going to improve the encyclopedicness of our coverage, you are probably reading it wrong. —David Eppstein (talk) 23:39, 4 May 2024 (UTC)
 * Personally, I think a detailed explanation about how to type the unicode glyph ⌀ in every environment seems out of scope for an article about the diameter of a circle. Explanations about how to insert unicode symbols on Mac, Windows, MS Word, etc. would probably be better to include somewhere such as Unicode input or (or in the off-wiki user manuals about specific software applications), rather than redundantly at every article mentioning a unicode glyph. –jacobolus (t) 00:51, 5 May 2024 (UTC)
 * A general description of how to type unicode would make sense at those targets. But those general descriptions are not likely to tell you for instance that an ß|eszet character can be obtained from option-s on Apple keyboards. Similarly, for this character the important part here is not how to use the compose key on Unix keyboards to obtain non-ASCII characters; it is that the compose code for this specific character is di. That is not even a "how to" piece of information. It is merely an association between two different systems of codes that otherwise might be difficult to find. If someone is looking up the diameter symbol, it might be because they remember that it has a compose code but not what it is. —David Eppstein (talk) 01:22, 5 May 2024 (UTC)
 * But that is the purpose of the Unicode input and compose key articles. It makes no sense to repeat the information at every article, with all the "if you have this keyboard, then do this; if you have that keyboard, then do that. Unless you have this other keyboard mapping. Or maybe a different code page". For example, if you have a QWERTZ keyboard, no gymnastics are required to get ß, you just press . To be fair, the Unicode input article is very thin on MacOS, but the solution is to fix that article once, not do it a hundred times in a hundred articles.
 * Clearly we have very different perceptions of the scope of NOTHOWTO, so I will ask at Wikipedia talk:What Wikipedia is not for a second opinion. --𝕁𝕄𝔽 (talk) 17:44, 5 May 2024 (UTC)
 * I'd have to agree with jacobolus that this seems out of scope of the article. Where would this stop, what of common mobile keyboards such as the iPhone, Samsung keyboard for Android, or GBoard, what of common accessibility keyboard. -- LCU A ctively D isinterested  «@» °∆t° 18:51, 5 May 2024 (UTC)
 * It makes no sense to argue that we should suppress this sourced information about how the unicode and compose-key-code are connected. It has nothing to do with NOTHOWTO because it is not even how to press the compose key, merely the fact that this character has this compose-key-code. It makes no sense to say that this information can only be in one place on the encyclopedia, because it is neither desirable not commonly followed to ensure that each encyclopedic claim appears only in one place. And it makes even less sense to say that this information should not appear here because other articles have the purpose of providing that information, when in fact this information appears nowhere on those other articles (and should not; we should not have an article providing the methods for inputting all possible unicode characters, as that would actually violate NOTHOWTO). As for your Whataboutism: we should only include sourced information about methods that are distinctive to this character, and not generic for all unicodes. For instance, the Apple keyboard (what I usually use) does not appear to have a shortcut for the diameter symbol (instead web sources suggest using the Danish slashed letter O, a different symbol) so we should not discuss how to get that symbol on Apple keyboards. —David Eppstein (talk) 19:18, 5 May 2024 (UTC)
 * But this isn't about reliable sources, it's about what should be included in this article. I sure reliable sources could be found on how to type the diameter sign on a multitude of different keyboards, that isn't a definitive reason to include the information in this specific article. -- LCU A ctively D isinterested  «@» °∆t° 21:10, 5 May 2024 (UTC)
 * Notice that before JMF's edits there was quite a lot of detail. [Edit: rm. re-quoted context that I just realized JMF already quoted at the top of this thread. I apparently skimmed right past it when reading before.]
 * If there's an article dedicated to the symbol ⌀, or to a group of related symbols, then it's fair enough to elaborate about it. I think it's off-topic / out of scope at an article about the diameter of a circle. I extended the discussion of LaTeX a bit, but frankly the whole discussion about that is also perhaps excessive here. It might be better to move this material to some other article about technical symbols, and just link it from here.
 * At this article, I would mention that there is a diameter symbol ⌀, describe how it is used to mean 'diameter' in technical drawings but rarely in other contexts, briefly mention what it's unicode name / code point is and that it's similar looking to the empty set symbol ∅, with relative appearance of the two varying from font to font. –jacobolus (t) 19:26, 5 May 2024 (UTC)
 * I have no interest in restoring that additional detail, but this discussion was sparked by the restoration of a single sourced line from it, the line about how the diameter symbol is coded as compose-d-i. I think it would be nonsensical to suppress that line. The rest of the information you quote is mostly generic to all unicodes, not specific to this article, and was correctly removed. —David Eppstein (talk) 19:28, 5 May 2024 (UTC)
 * I don't think we currently have any article about writing conventions and symbols used in technical drawings, but I think all of this info would be more relevant at such an article than here. –jacobolus (t) 20:47, 5 May 2024 (UTC)
 * Even if there was a standalone article about that symbol, the full instructions of how to type it would be out of scope. Instead, a page about, for example, LaTeX, it would be fair to include a list of codes and brief instructions how they are entered on various systems, such that there is only one place on WP where these instructions would make sense. I absolutely agree the inclusion here fails NOTHOWTO. — M asem  (t) 20:04, 5 May 2024 (UTC)
 * I also agree; this is exactly what NOTHOWTO indicates should not go in articles. If any portion of an article reads like a tutorial or manual, it almost certainly violates NOTHOWTO. That doesn't mean the information is of no value, it's just out of scope for Wikipedia. Seraphimblade Talk to me 20:13, 5 May 2024 (UTC)
 * Thanks, Jacobolus, for confusing the issue by providing a big example of stuff not to include that everyone can agree not to include so that we have no idea whether the responses are about that big example or about the content actually under dispute. User:Masem and User:Seraphimblade, can you be more specific about whether it is off-topic to state the unicode code point of a symbol on an article (or in this case the target of a redirect diameter symbol) about that symbol (without detail about how one types unicode code points)? If not, can you explain what you think is different about stating the compose code abbreviation for the same symbol (again, without detail about how one types compose codes)? —David Eppstein (talk) 20:21, 5 May 2024 (UTC)
 * The sarcasm is entirely unnecessary. Thanks. –jacobolus (t) 20:38, 5 May 2024 (UTC)
 * Yes, and I don't appreciate being told I'm confused. If there is any material telling the reader "Here's instructions for how you _________", large or small, that is out of scope for the article. That includes the long digression, and it also includes the current "It can be obtained in Unix-like operating systems using Compose-d-i", which also needs to be removed. I do actually read things before I comment on them, and I was not in any way confused. If I was, I would have asked for clarification. Seraphimblade Talk to me 20:42, 5 May 2024 (UTC)
 * So you object to saying that people can do things, even in passive voice? So on ballot, you would object to the line "Each voter uses one ballot, and ballots are not shared." because that might be interpreted as instructions to readers on how to vote? That is a completely nonsensical view of NOTHOWTO. It is frequently the case that ways of doing things are topics of encyclopedic content. "How" is one of the fundamental questions encyclopedias answer, along with "what", "when", "where", "why", and "who". Is it the verb "can be obtained" that you object to? If we rephrased it in a way that eliminated any possibility of being interpreted as an instruction, would that satisfy you? Something like
 * It has the compose sequence compose-d-i.
 * ? —David Eppstein (talk) 20:48, 5 May 2024 (UTC)
 * A discussion of how the symbol is made on keyboards might be in scope for an article on the symbol itself, if it's notable enough for one. But it is excess detail for an article about the concept of diameter in general. Seraphimblade Talk to me 20:51, 5 May 2024 (UTC)
 * I'm not too worried about the scope or details of the "nothowto" policy per se, and focusing on that seems like a distraction. The question for me is: Should we expect that someone trying to type the symbol ⌀ in Linux should be looking for that info in a Wikipedia article about the diameter of a circle, and should we expect any substantial portion of the readers of an article about the diameter of a circle to be interested in how to type the symbol ⌀ in Linux? –jacobolus (t) 20:55, 5 May 2024 (UTC)
 * In fact I am worried about nothowto, because the subject of my professional research is algorithms, and an obtuse flat never-on-Wikipedia interpretation of nothowto would seem to forbid all articles about algorithms. When interpreted as meaning "don't write in the style of a user guide" (as your long block example here did), nothowto is fine. When interpreted as meaning "suppress any information that readers might use to learn how to do things", it is bad and should be fought hard at all turns. —David Eppstein (talk) 21:08, 5 May 2024 (UTC)
 * Well, I don't think there is any harm if this article, for example, explains how the diameter of a circle is calculated (at least in general, though not step-by-step instructions). That's an entirely valid thing to be in an article about diameter. But this article is not about the diameter symbol. Noting that there is a symbol for diameter is valid in this article, but detail on how to type it on various operating systems (and why just *nix? Why not Windows, or MacOS/iOS, or anything else?) is not in the scope of this article. Seraphimblade Talk to me 21:20, 5 May 2024 (UTC)
 * An algorithm is exactly "step-by-step instructions". You are still taking a position I abhor, that any form of step-by-step instructions are forbidden. One cannot describe an algorithm accurately without stating it in the form of step-by-step instructions. You are parroting the bad side of nothowto, the side that is about content rather than style. —David Eppstein (talk) 21:29, 5 May 2024 (UTC)
 * @David Eppstein I feel like you are ignoring people's point to focus on straw-man hypotheticals. Nobody is suggesting removing descriptions of algorithms from articles about those algorithms. We're talking about removing detailed descriptions about input of a symbol which was shoehorned into a substantially unrelated article.
 * My proposal to resolve this would be to create a stub article diameter symbol, and move this information there. –jacobolus (t) 22:47, 5 May 2024 (UTC)
 * If you think this is a strawman then you need to explain it to me in a way that makes sense.
 * Currently we have a lot of people arguing that a code for a character (the code compose-d-i) should be removed, using NOTHOWTO as justification. There is nothing user-guide-like in the way the code is described. It does not say anything about pressing keys. It does not even tell readers what a compose sequence might be used for. It just states the sequence. Nevertheless, we still have NOTHOWTO invoked as the justification.
 * I don't understand it. If NOTHOWTO is merely the guidance not to write like a user guide, we are already following it. The only other explanation I can find to motivate these comments is that compose-sequences are things people use to do things, and that NOTHOWTO forbids us from writing anything that could be interpreted as describing how people do things. So if a code is not merely a code, but also a sequence of keypresses, then we must suppress that code, because people might press those keys in that sequence, and then they would learn something about how to do things from the encyclopedia. We can't have that. It is that interpretation that I am strongly against.
 * Maybe there is some other motivation that I am missing. Maybe there is some other explanation for why mentioning a character code is forbidden when that code happens to be a compose sequence but allowed when that code happens to be a unicode; I asked above for something that would differentiate those two cases but everyone I asked avoided that topic. If you can provide an explanation, please do.
 * As for moving it to a separate stub: I am not opposed, but I am also not convinced that (even after my improvements to use several book sources) we have enough depth of coverage to make a separate article that would survive an AfD. —David Eppstein (talk) 23:15, 5 May 2024 (UTC)
 * Unicode is universal and XCompose is not. Remsense  诉  23:20, 5 May 2024 (UTC)
 * Would that sentence be any more meaningful if you wrote "Unicode is universal and EBCDIC is not" or "Unicode is universal and non-numeric html entities are not"? What is the relevance of universality here? —David Eppstein (talk) 23:33, 5 May 2024 (UTC)
 * I am not sure any more. I think your point below about text encoding broadly construed is worthwhile, which is why I was mulling the viability of a dedicated reference page that could list this information in a way that suits readers and is WP:DUE. If someone is interested in the code for one symbol, isn't it likely they would be interested in the code for several related symbols? Remsense  诉  23:38, 5 May 2024 (UTC)
 * At one point I thought we had this example, but it is one thing to say "Chicken soup is typically made from chicken broth, chicken meat, noodles, and a variety of spices", and "You make chicken soup by adding 1 cup of cut chicken to 2 quarts of chicken stock, then 1/2 tablespoon salt...(etc.)". The first is an encyclopedic line, just as saying the diameter symbol has a specific Unicode number or LaTex symbol, or how a typical democratic vote process works; verses detailed instructions for how to enter the symbol or explaining how one locates their specific voting place and what they are expected to do there. M asem  (t) 20:57, 5 May 2024 (UTC)
 * Also, as someone who loves their compose key to death: pretending WP:NOTHOWTO doesn't exist for a second: their use is simply not prevalent enough to include on almost any article not directly related to computer input, full stop. Remsense  诉  21:00, 5 May 2024 (UTC)
 * Certainly if this article were only about diameters, and not about the diameter symbol, I would not include it. But the fact remains that this is the only Wikipedia article about the diameter symbol. We could discuss splitting it off into a separate article but that would require better sourcing than we currently have. —David Eppstein (talk) 21:11, 5 May 2024 (UTC)
 * The article that best includes info on the diameter symbol is Glossary of mathematical symbols, not this article. M asem (t) 21:18, 5 May 2024 (UTC)
 * Perhaps you can rephrase that in a way that does not imply that every claim on Wikipedia can only appear in a single article. Because I have good faith that you would not take such an extreme position, but I am not getting that from your comment here. How is a reader, looking up diameter symbol, to guess that this information might instead be found somewhere else (in the bottom of a locked filing cabinet stuck in a disused lavatory with a sign on the door saying "Beware of the Leopard")?
 * Do you, perhaps, mean instead that all the details about the diameter symbol, and the redirect target for diameter symbol, would all be better moved to that glossary? So that readers looking up diameter symbol would find that information there, and not come here at all? But that glossary does not appear to list even the unicodes for its entries (it is more about notation than about characters). —David Eppstein (talk) 21:21, 5 May 2024 (UTC)
 * Just because a plausible redirect exists does not mean by itself that the target of the redirect is to be considered a distinct subject upon scrutiny. Also, here's a direct answer to the question: how about a hatnote to, or an equivalent that does effectively juxtapose this information. That seems like a solution everyone present would be mighty happy with. Remsense  诉  21:26, 5 May 2024 (UTC)
 * So you are proposing to rewrite glossary of mathematical symbols in its entirety, to discuss symbol encodings for all the symbols it describes? Or are you proposing to sweep the encoding under the rug by saying it can only go on some other article where it cannot go and therefore we cannot discuss encodings at all, anywhere? Not even the unicode? —David Eppstein (talk) 21:32, 5 May 2024 (UTC)
 * Possibly the former, possibly a new page, I am not sure. (Glossary is a coherent type of reference work, why not 'technical glossary'?) Not the latter, as I think the UTF encoding is DUE for any section discussing symbols. Remsense  诉  21:38, 5 May 2024 (UTC)
 * This is not really a "mathematical symbol". I have personally never seen this symbol used in a mathematical work (though it's certainly possible someone has somewhere), after reading lots and lots of works about circles and spheres. It's a symbol used to indicate measurements in technical drawings.
 * The ideal home for this would be an article about the typography of technical drawings, but we don't currently have one. –jacobolus (t) 23:50, 5 May 2024 (UTC)
 * Well, not only technical drawings. See the sentence about camera lens filter diameter markings. —David Eppstein (talk) 23:59, 5 May 2024 (UTC)
 * Maybe to be more precise: this symbol is an abbreviation for the word "diameter" in the context of engineering/technical materials including blueprints, specification sheets, manuals, ... Maybe would be a reasonable home. –jacobolus (t) 00:03, 6 May 2024 (UTC)
 * That...makes more sense than in an article about diameters in geometry, actually. —David Eppstein (talk) 00:33, 6 May 2024 (UTC)
 * There's a pretty clear distinction between these two examples: the process of long division is itself the subject of the latter example. The subject of this article is not that of Input methods, and these inclusions seem parochial to me, as if seeking to address what is seen as an omission in how the subject has been described to date. If this were apropos for the subject Diameter, our sources would include something like it; instead it is clear to me they were added mostly because they seemed a "bonus" for the reader, rather than reflecting the subject as covered in sources. Remsense  诉  20:50, 5 May 2024 (UTC)
 * The subject of diameter symbol is, exactly, the diameter symbol. It happens to be a redirect, but it still needs to be treated encyclopedia at that redirect target, like our other content about symbols. —David Eppstein (talk) 21:05, 5 May 2024 (UTC)
 * The subject is diameter, with the symbol not being sufficiently distinct to warrant its own article. This seems a trivial understanding of N and DUE. Remsense  诉  21:14, 5 May 2024 (UTC)
 * The subject is diameter, with the symbol not being sufficiently distinct to warrant its own article. This seems a trivial understanding of N and DUE. Remsense  诉  21:14, 5 May 2024 (UTC)

Given that it was I who invited second opinions on the scope of NOTHOWTO, may I make clear that my concern is for the general point, not specifically about the concept of 'diameter' and its specific symbol. So may I choose a better example that I think will make clearer the different perspective held by David E and me: the ß|eszet character (ß). As I understand David's view, that article should contain information on how to enter it if you don't have a QWERTZ keyboard. My view is that readers should be referred for that information to an article that specialises in such questions, for all non-ASCII characters. Does that illustrate the issue more clearly? --𝕁𝕄𝔽 (talk) 22:31, 5 May 2024 (UTC)

1.(computing) The way in which symbols are mapped onto bytes, e.g. in the rendering of a particular font, or in the mapping from keyboard input into visual text. 2.A conversion of plain text into a code or cypher form (for decoding by the recipient)."
 * Yes. My position is that not much more than the UTF codepoint should be explicated in generalized articles or sections on symbols themselves, and that a specialized article of some kind should be referenced instead. Remsense  诉  22:43, 5 May 2024 (UTC)
 * JMF, that is a mischaracterization of my view. I am not particularly interested in providing a compendium of methods for finding and entering the eszet character on different systems; that might indeed fall afoul of NOTHOWTO. But, when we are writing about a character, we should write about its encoding in notable systems for encoding characters. Unicode is one such system, but not the only one. For instance, the eszet article also mentions its encoding as an html entity. I have not ever used compose sequences, but I was under the impression that compose sequences can also be thought of as a system for encoding characters, at least temporarily before they are translated into something more suitable for file storage. Is it not a notable system for encoding characters? Does the fact that it can be entered directly somehow taint it? If I enter unicodes directly on my keyboard using numeric codes, does it taint them, too, so that they could not be mentioned either? —David Eppstein (talk) 23:28, 5 May 2024 (UTC)
 * I entirely disagree with this one JMF. How Eszet is handled by various systems (the whole history of the treatment of this character by systems from 19th century telegraphs up through present computer software) is clearly in scope for an article about Eszet, and coverage should be as comprehensive as any editor is motivated to track down reliable sources for. This shows pretty well why WP:NOTHOWTO is not really the right reason for rejecting this information here. If we want a little wiki-insider abbreviation, I would list WP:DUE and WP:COATRACK. –jacobolus (t) 23:54, 5 May 2024 (UTC)
 * @David Eppstein perhaps my failed attempt to summarise your position may help explain our difference of view. But first a clarification: the html code is not unique, it is just another way of presenting the Unicode code-point value. Nor are compose sequences unique: these too are ways of presenting or requesting the unicode code-point – no different in concept to using  or . [Diameter, oth, is special because LaTeX and AutoCAD are not using Unicode, they are drawing the glyph in a different way. These are unique encoding methods.]
 * @Jacobolus, you illustrate why I chose a new example – because it was getting sidetracked into discussing the main body of the article. In each case, there is a valid article about the concept and/or history behind character. But this discussion is on encoding(s) of the character. In the case of Eszet, there is only one – Unicode (including its integrated predecessor, ISO Latin-1). The dispute is whether the section should go on the explain how to type that symbol into your essay. 𝕁𝕄𝔽 (talk) 08:33, 6 May 2024 (UTC)
 * @David Eppstein, just to clarify the html question, take another example: basis point . You can write it as &#x2031, &#8241 or the mnemonic &pertenk: all are equally ways to represent the same binary code recognised by the text rendering engine. (As before, LaTeX and AutoCAD use very different engines.) 𝕁𝕄𝔽 (talk) 11:51, 6 May 2024 (UTC)
 * This is a poor example in my opinion. The per ten thousand sign is not actually used for basis points. It seems self evident to me that discussion of this symbol per se belongs at percent sign, not at basis point. If placed in a section of percent sign, it would be fine in my opinion to discuss various ways of encoding the symbol in HTML, etc. Discussion of the ins and outs of this symbol seems clearly out of scope for the article basis point as used in finance, where this symbol never appears. –jacobolus (t) 14:45, 6 May 2024 (UTC)
 * Re the number 0.0001, how is your comment remotely relevant to the question of what the encoding section should contain? --𝕁𝕄𝔽 (talk) 17:07, 6 May 2024 (UTC)
 * In my opinion, text encoding and input is clearly directly relevant to an article about percent sign or ‱ as a symbol per se, but is entirely off topic and inappropriate in an article about basis points. –jacobolus (t) 18:53, 6 May 2024 (UTC)
 * To me, all are equally valid ways of representing the glyph and its associated semantics. In the case of html entities, I believe they are defined to be shortcuts for unicodes. But in general there is no justification for conflating glyphs with unicodes. A system of coding glyphs may be intended to be used for translation into another system of coding glyphs (as non-numeric html entities to unicodes), it may directly represent another system of coding glyphs (as numeric html entities represent unicodes), or it may stand on its own. It may be intended to be used for human input (compose codes, Apple option codes), it may be intended only for internal storage (binary-represented unicodes), or it may be intended only for output (whatever coding was sent to a Compugraphic machine, etc). But to me the intended use of a system of coding glyphs is secondary to the fact that it is an organized system of coding glyphs. —David Eppstein (talk) 17:33, 6 May 2024 (UTC)
 * But in general there is no justification for conflating glyphs with unicodes. I agree completely! neither LaTeX nor AutoCAD use Unicode  for the diameter glyph –  and indeed the same is true in LaTeX for all the mathematical symbols.
 * &#x2031, ‱ and ‱ are identical and are the way to write the Unicode code-point in HTML – that is how its syntax works. They are not alternatives to Unicode, they are Unicode. Of course the code could be translated into another system but that is seriously out of scope, IMO. I don't understand your it may stand on its own. The, , , CharMap selection etc are input methods, designed to select the Unicode number. Whether that number is stored in a database (to represent a glyph) or is used to display or print it is not obviously significant: once it is captured, you do what you like with it.
 * I'm afraid that I don't follow your last point? Is it relevant to whether it is appropriate or not, to list in the #Encoding section of every article about every glyph, the details of all the input methods that can be used to encode it? --𝕁𝕄𝔽 (talk) 19:04, 6 May 2024 (UTC)
 * I don't understand why you want to single out input methods as not being encodings. They are encodings. The fact that they are (usually) immediately translated to a different encoding doesn't change that fact. —David Eppstein (talk) 20:19, 6 May 2024 (UTC)
 * Are we at cross-purposes with our use of the word encoding? According to Wiktionary:
 * "encoding (plural encodings)
 * I have been using it in the first sense, the mapping of a human-readable symbol onto a machine-readable binary string. Are you using the second? (the process by which that mapping is achieved). --𝕁𝕄𝔽 (talk) 22:59, 6 May 2024 (UTC)
 * "the mapping from keyboard input into visual text" is directly there in your first definition. I really don't understand the confusion. –jacobolus (t) 23:24, 6 May 2024 (UTC)
 * But also, a compose sequence really is a mapping between symbols and sequences of bytes. As in, it corresponds the diameter symbol discussed in this article to the sequence of ASCII bytes d (100) i (105). To use this embedded within normal ASCII or Latin1 you would need some sort of convention for how to express the compose symbol but there are plenty of octets free as control symbols used for that.
 * Also, that is a ridiculously overspecific definition. Are six-bit or seven-bit ASCII (both in use on DEC 36-bit architectures in the 1970s and 1980s) somehow not encodings because they do not use 8-bit bytes? What about 10-bit encodings on punched cards? —David Eppstein (talk) 00:28, 7 May 2024 (UTC)
 * I am with David here, this distinction as presented seems arbitrary in the context of what it means for a page about a grapheme. My notion was more about the comparative use of encodings, i.e. pretty much just Unicode. Remsense  诉  01:26, 7 May 2024 (UTC)
 * No, the article Eszett can (if someone tracks down reliable sources) discuss the history of the appearance of Eszett on various computer keyboards, whether and how it has been type-able when it didn't appear directly, how else it might be input if not type-able, how it was encoded (and not just in Latin-1 but also in whatever other character encoding), and so on. All of this is clearly encyclopedic. In an article scoped to be directly about the diameter symbol, such information would also be fine, in my opinion. –jacobolus (t) 14:37, 6 May 2024 (UTC)
 * Re Eszett, the material you have in mind would be a section in its own right. If you want to write such a section, you may find what you need at Schreibmaschine and QWERTZ. Again, how is it relevant to encoding and input methods? --𝕁𝕄𝔽 (talk) 17:07, 6 May 2024 (UTC)

Need Figure for Convex Shape in the Plane
The intro contains the following: "For a convex shape in the plane, the diameter is defined to be the largest distance that can be formed between two opposite parallel lines tangent to its boundary..." I haven't been able to decipher that. (I'm not a mathematician.) Sure would be helpful if someone added a figure to illustrate that. I picture the convex shape being a curve that is a fourth of a circle. Don't know what the "boundary" is, or how such a shape has two tangent lines that are parallel. Thanks!--Christopher King (talk) 21:38, 22 June 2024 (UTC)

title: Talk:Diameter


text:
Fortune cookie

A fortune cookie is a crisp and sugary cookie wafer made from flour, sugar, vanilla, and sesame seed oil with a piece of paper inside, a "fortune", an aphorism, or a vague prophecy. The message inside may also include a Chinese phrase with translation and/or a list of lucky numbers used by some as lottery numbers. Fortune cookies are often served as a dessert in Chinese restaurants in the United States, Canada, Australia, and other countries, but they are not Chinese in origin. The exact origin of fortune cookies is unclear, though various immigrant groups in California claim to have popularized them in the early 20th century. They most likely originated from cookies made by Japanese immigrants to the United States in the late 19th or early 20th century. The Japanese version did not have the Chinese lucky numbers and were eaten with tea.

Translations of the name
Globally, the cookies are generally called by the English term fortune cookies, being American in origin.

There is no single accepted Chinese name for the cookies, with a large variety of translations being used to describe them in the Chinese language, all of which being more-or-less literal translations of the English "fortune cookie". Examples include: 幸运籤饼 xìngyùn qiān bǐng "good luck lot cookie", 籤语饼 qiān yǔ bǐng "fortune words cookie", 幸运饼 xìngyùn bǐng "good luck cookie", 幸运籤语饼 xìngyùn qiān yǔ bǐng "lucky fortune words cookie", 幸运甜饼 xìngyùn tián bǐng "good luck sweet cookie", 幸福饼干 xìngfú bǐnggān "good luck biscuit", or 占卜饼 zhānbǔ bǐng "divining cookie".

History
As far back as the 19th century, a cookie very similar in appearance to the modern fortune cookie was made in Kyoto, Japan, and there is a Japanese temple tradition of random fortunes, called omikuji. The Japanese version of the cookie differs in several ways: they are a little bit larger; are made of darker dough; and their batter contains sesame and miso rather than vanilla and butter. They contain a fortune; however, the small slip of paper was wedged into the bend of the cookie rather than placed inside the hollow portion. This kind of cookie is called tsujiura senbei (辻占煎餅) and is still sold in some regions of Japan, especially in Kanazawa, Ishikawa. It is also sold in the neighborhood of Fushimi Inari-taisha shrine in Kyoto.

Makoto Hagiwara of Golden Gate Park's Japanese Tea Garden in San Francisco is reported to have been the first person in the U.S. to have served the modern version of the cookie when he did so at the tea garden in the early 1900s. The fortune cookies were made by a San Francisco bakery, Benkyodo.

David Jung, founder of the Hong Kong Noodle Company in Los Angeles, has made a competing claim that he invented the cookie in 1918. San Francisco's Court of Historical Review attempted to settle the dispute in 1983. During the proceedings, a fortune cookie was introduced as a piece of evidence with a message reading, "S.F. Judge who rules for L.A. Not Very Smart Cookie". A federal judge of the Court of Historical Review, from San Francisco themselves, determined that the cookie originated with Hagiwara and the court ruled in favor of San Francisco. Subsequently, the city of Los Angeles condemned the decision.

Seiichi Kito, the founder of Fugetsu-do of Little Tokyo in Los Angeles, also claims to have invented the cookie. Kito claims to have gotten the idea of putting a message in a cookie from Omikuji (fortune slip) which are sold at temples and shrines in Japan. According to his story, he sold his cookies to Chinese restaurants where they were greeted with much enthusiasm in both the Los Angeles and San Francisco areas, before spreading.

Up to around World War II, fortune cookies were known as "fortune tea cakes"—likely reflecting their origins in Japanese tea cakes.

Fortune cookies moved from being a confection dominated by Japanese-Americans to one dominated by Chinese-Americans sometime around World War II. One theory for why this occurred is because of the Japanese American internment during World War II, which forcibly put over 100,000 Japanese-Americans in internment camps, including those who had produced fortune cookies. This gave an opportunity for Chinese manufacturers.

Fortune cookies before the early 20th century were all made by hand. The fortune cookie industry changed dramatically after the fortune cookie machine was invented by Edward Louie in the late 1960s. The machine allowed for mass production of fortune cookies which subsequently allowed the cookies to drop in price to become the novelty and courtesy dessert many Americans are familiar with after their meals at most Chinese restaurants today.

Manufacturers
There are approximately 3 billion fortune cookies made each year globally, the majority of them consumed in the US. The largest manufacturer of the cookies is Wonton Food, Inc., headquartered in Brooklyn, New York. They make over 4.5 million fortune cookies per day. Other large manufacturers are Baily International in the Midwest and Peking Noodle in Los Angeles. There are other smaller, local manufacturers including Tsue Chong Co. in Seattle, Keefer Court Food in Minneapolis, Sunrise Fortune Cookie in Philadelphia, and Golden Gate Fortune Cookie Factory in San Francisco. Many smaller companies will also sell custom fortunes.

Manufacturing processes vary, but they generally follow the same procedure. The ingredients (typically made with a base of flour, sugar, vanilla, and sesame seed oil) are mixed in a large tank and squirted onto fast moving trays. These function like a conveyor belt and are heated to cook the dough. Cookies are compressed with round hot plates to shape and cook them. The cookies bake for approximately one minute and are reshaped. They can be mechanically shaped or folded by hand. When automated, a machine folds the cookie into the correct orientation with the fortune inside. Cooled and hardened cookies are sealed in plastic wrappers, which are inspected before being shipped. Today, most cookies are produced in the United States with the biggest factory located in Brooklyn.

Marketing
The message inside may include a list of lucky numbers used by some as lottery numbers; since relatively few distinct messages are printed, in the recorded case where winning numbers happened to be printed, the lottery had an unexpectedly high number of winners sharing a prize. Authorities briefly investigated Wonton Food in 2005, after 110 Powerball lottery players won about $19 million after using the "lucky numbers" on the back of fortunes.

Fortune cookies are sometimes used for special marketing promotions. For example, the film Kung Fu Panda 3 was promoted by putting quotations from the protagonist of the film on fortune cookie slips.

In 1989, fortune cookies were reportedly imported into Hong Kong and sold as "genuine American fortune cookies". Wonton Food attempted to expand its fortune cookie business into China in 1992, but gave up after fortune cookies were considered "too American".

Nutrition
Cookies from different manufacturers have different ingredients and nutritional content. One cookie typically contains around 20 to 30 kcal of food energy and 5–7 g of total carbohydrates. A cookie may have sugar varying from 0–3 g, between 2–8 mg of sodium, and may have significant (compared to their size) amounts of iron or protein. The small size means they have little overall nutritional value.

Around the world
Fortune cookies, while largely an American item, have been served in Chinese restaurants in Australia, Argentina, Brazil, Canada, France, Germany, India, Italy, Mexico, New Zealand, Norway, Singapore, United Kingdom, United Arab Emirates as well as other countries. In Peru, they are served in the chifas, Chinese-Peruvian fusion food restaurants.

There are also multi-cultural versions of the fortune cookie. For instance, the Mexican version of the fortune cookie, called the "Lucky Taco", is a red taco-shaped cookie with a fortune inside. The same company that makes the Lucky Taco also makes a "Lucky Cannoli", inspired by Italian cannolis.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Fortune cookie


text:
Candiru (fish)

Candiru (Vandellia cirrhosa), also known as cañero, toothpick fish, or vampire fish, is a species of parasitic freshwater catfish in the family Trichomycteridae native to the Amazon basin where it is found in the countries of Bolivia, Brazil, Colombia, Ecuador, and Peru.

The definition of candiru differs between authors. The word has been used to refer to only Vandellia cirrhosa, the entire genus Vandellia, the subfamily Vandelliinae, or even the two subfamilies Vandelliinae and Stegophilinae.

Although some candiru species have been known to grow to a size of 40 cm in length, others are considerably smaller. These smaller species are known for an alleged tendency to invade and parasitise the human urethra and other bodily openings; however, despite ethnological reports dating back to the late 19th century, the first documented case of the removal of a candiru from a human urethra did not occur until 1997, and even that incident has remained a matter of controversy.

Description
Candirus are small fish. Members of the genus Vandellia can reach up to 17 cm in standard length, but some others can grow to around 40 cm. Each has a rather small head and a belly that can appear distended, especially after a large blood meal. The body is translucent, making it quite difficult to spot in the turbid waters of its home. There are short sensory barbels around the head, together with short, backward pointing spines on the gill covers.

Location and habitat
Candirus (Vandellia) inhabit the Amazon and Orinoco basins of lowland Amazonia, where they constitute part of the Neotropical fish fauna. Candirus are hematophagous and parasitize the gills of larger Amazonian fishes, especially catfish of the family Pimelodidae (Siluriformes).

Alleged attacks on humans
Although lurid anecdotes of attacks on humans abound, only one somewhat questionable case has evidence behind it, and some alleged traits of the fish have been discredited as myth or superstition. It is likely that, while the fish's spines can cause physical trauma, it merely poses as much danger of actually entering a human as any other fish of its size.

Historical accounts
The earliest published report of candiru attacking a human host comes from German biologist C. F. P. von Martius in 1829, who never actually observed it, but rather was told about it by an interpreter relaying the speech of the native people of the area, who reported that men would tie ligatures around their penises while going into the river to prevent this from happening. Other sources also suggest that other tribes in the area used various forms of protective coverings for their genitals while bathing, though it was also suggested that these were to prevent bites from piranha. Martius also speculated that the fish were attracted by the "odor" of urine. Later experimental evidence has shown this to be false, as the fish actually hunt by sight and have no attraction to urine at all.

Another report, from French naturalist Francis de Castelnau in 1855, relates an allegation by local Araguay fisherman, saying that it is dangerous to urinate in the river as the fish "springs out of the water and penetrates into the urethra by ascending the length of the liquid column." While Castelnau himself dismissed this claim as "absolutely preposterous," and the fluid mechanics of such a maneuver defy the laws of physics, it remains one of the more stubborn myths about the candiru. It has been suggested this claim evolved out of the real observation that certain species of fish in the Amazon will gather at the surface near the point where a urine stream enters, having been attracted by the noise and agitation of the water.

In 1836, Eduard Poeppig documented a statement by a local physician in Pará, known only as Dr. Lacerda, who offered an eyewitness account of a case where a candiru had entered a human orifice. However, it was lodged in a native woman's vagina, rather than a male urethra. He relates that the fish was extracted after external and internal application of the juice from a Xagua plant (believed to be a name for Genipa americana). Another account was documented by biologist George A. Boulenger from a Brazilian physician, named Dr. Bach, who had examined a man and several boys whose penises had been amputated. Bach believed this was a remedy performed because of parasitism by candiru, but he was merely speculating, as he did not speak his patients' language. American biologist Eugene Willis Gudger noted that the area which the patients were from did not have candiru in its rivers, and suggested the amputations were much more likely the result of having been attacked by piranha.

In 1891, naturalist Paul Le Cointe provides a rare first-hand account of a candiru entering a human body, and like Lacerda's account, it involved the fish being lodged in the vaginal canal, not the urethra. Le Cointe supposedly removed the fish himself, by pushing it forward to disengage the spines, turning it around and removing it head-first.

However, the veracity of both Le Cointe's and Poeppig's accounts are questionable, due to a trend of Europeans from various careers residing in Brazil including scientists, "explorers, medical men, and missionaries" regularly using exaggerated accounts of native people to advance their economic and social status through writing and building rapport with others with similar positions.

Gudger, in 1930, noted there have been several other cases reported wherein the fish was said to have entered the vaginal canal, but not a single case of a candiru entering the anus was ever documented. According to Gudger, this lends credence to the unlikelihood of the fish entering the male urethra, based on the comparatively small opening that would accommodate only the most immature members of the species.

Modern cases
To date, there is only one documented case of a candiru entering a human urethra, which took place in Itacoatiara, Brazil, in 1997. In this incident, the victim (a 23-year-old man named Silvio Barbossa, also known as "F.B.C.") claimed a candiru "jumped" from the water into his urethra as he urinated while thigh-deep in a river. After traveling to Manaus on October 28, 1997, the victim underwent a two-hour urological surgery by Dr. Anoar Samad to remove the fish from his body.

In 1999, American marine biologist Stephen Spotte traveled to Brazil to investigate this particular incident in detail. He recounts the events of his investigation in his book Candiru: Life and Legend of the Bloodsucking Catfishes. Spotte met Dr. Samad in person and interviewed him at his practice and home. Samad gave him photos, the original VHS tape of the cystoscopy procedure, and the actual fish's body preserved in formalin as his donation to the National Institute of Amazonian Research. Spotte and his colleague Paulo Petry took these materials and examined them at the institute, comparing them with Samad's formal paper. While Spotte did not overtly express any conclusions as to the veracity of the incident, he did remark on several observations that were suspicious about the claims of the patient and/or Samad himself.

 * According to Samad, the patient claimed "the fish had darted out of the water, up the urine stream, and into his urethra." While this is the most popularly known legendary trait of the candiru, according to Spotte it has been known conclusively to be a myth for more than a century, as it is impossible because of simple fluid physics.
 * The documentation and specimen provided indicate a fish that was 133.5 mm in length and had a head with a diameter of 11.5 mm. This would have required significant force to pry the urethra open to this extent. The candiru has no appendages or other apparatus that would have been necessary to accomplish this, and if it were leaping out of the water as the patient claimed, it would not have had sufficient leverage to force its way inside.
 * Samad's paper claims the fish must have been attracted by the urine. This belief about the fish has been held for centuries, but was discredited in 2001. While this was merely speculation on Samad's part based on the prevailing scientific knowledge at the time, it somewhat erodes the patient's story by eliminating the motivation for the fish to have attacked him in the first place.
 * Samad claimed the fish had "chewed" its way through the ventral wall of the urethra into the patient's scrotum. Spotte notes that the candiru does not possess the right teeth or strong enough dentition to have been capable of this. Additionally, the fish would most likely have died before it could have chewed even a somewhat large part of what was needed to reach it.
 * Samad claimed he had to snip the candiru's grasping spikes off in order to extract it, yet the specimen provided had all its spikes intact.
 * The cystoscopy video depicts traveling into a tubular space (presumed to be the patient's urethra) containing the fish's carcass and then pulling it out backwards through the urethral opening, something that would have been almost impossible with the fish's spikes intact.

When subsequently interviewed, Spotte stated that even if a person were to urinate while "submerged in a stream where candiru live", the odds of that person being attacked by candiru are "(a)bout the same as being struck by lightning while simultaneously being eaten by a shark."

title: Candiru (fish)