Talk:Transversality theorem

⫛

The symbol ⫛ redirects here, and although it is used, it is never defined. Dpleibovitz (talk) 07:09, 13 February 2020 (UTC)

The definition of the "pitchfork" ⫛ is in Transversality theorem § Previous definitions:

Let $f\colon X\rightarrow Y$ be a smooth map between smooth manifolds, and let $Z$ be a submanifold of $Y$. We say that $f$ is transverse to $Z$, denoted as $f\pitchfork Z$, if and only if for every $x\in f^{-1}\left(Z\right)$ we have that

$\operatorname {im} \left(df_{x}\right)+T_{f\left(x\right)}Z=T_{f\left(x\right)}Y$.

Note the emphasized part "denoted as $f\pitchfork Z$". The pitchfork appears in TeXified math fragments only, and this means that you get zero results if you use the search function of your browser to look for the pitchfork character ⫛ on the Transversality theorem page. I don't know how to fix this. – Tea2min (talk) 08:22, 13 February 2020 (UTC)

Dubious

We have no source (I didn't look in all the unmarked sources cited on this page) for ⋔ being used as a symbol for this. The only example I can find is this wikipedia page, which is probably using it as a typographical approximation (I also do not know how to fix the problem mentioned in #⫛ above, because I'm not a big wikipedia math guy). In fact, the unicode block that documents it lists another name for it as "proper intersection", suggesting a different use (I guess like proper subset has a notation, so does proper intersection). However, it's possible that it's used for both.

If this is spurious, we should remove ⋔ from this page, remove the redirect from ⋔ to this page, and fix wikt:⋔ while we're at it (propose that entry for deletion?) Dingolover6969 (talk) 05:31, 18 May 2026 (UTC)

Guillemin and Pollack appear to use something like ${\bar {\pitchfork }}$ for this (it may be provided in some latex packages as \topfork). This is uncommon however, most authors just use \pitchfork by itself, e.g., .The unicode character is U+2ADB "TRANSVERSAL INTERSECTION". I think transversal intersection is probably a better redirect target for the glyph. Sławomir Biały (talk) 06:43, 18 May 2026 (UTC)

@Dingolover6969 Based on your message on the Project Mathematics talk page,he answer below assume that the question is mostly about ⋔ vs ⫛, rather than about transversal vs proper intersection or about the name of the unicode character ⫛:

The "correct" symbol is an intersection sign with a vertical bar. Here on Wikipedia, there are two main ways to write the intersection sign:

• $\cap$ — arguably the most common in math articles at that level. When that symbol is used, $\pitchfork$ is the "correct" symbol. It does not matter that the LaTeX command is called "pitchfork".
• ∩ — in that case, I guess the exact way the way the symbol is rendered might depend on installed fonts on the user's setup (?). On my computer, ∩ / ⋔ and ∩ / ⫛ look similar enough that I guess both could be used... But if you want to use ⫛ everywhere, please go for it.

Yet another way that the symbol could be rendered is as ⫛ — i.e. using the unicode symbol directly without enclosing it in a "math" environment. But this is not recommended. It's better to convert formulas typeset this way to either <math>\pitchfork</math> or {{math|⫛}}. Also, note that ⫛ does not look at all like a ∩ with a vertical line (at least not on my computer), whereas ⋔ does: compare ∩ / ⋔ vs ∩ / ⫛. So in that case, I guess the notation ⋔ is more "correct" than ⫛ — despite what the unicode characters are named... But, again: this discussion doesn't matter anyway, because mathematical formulas should be typeset using <math></math> or {{math|}}.

If the question was actually about using other notations for transversal intersection or about something else, let me know so I can adapt my answer. Malparti (talk) 11:42, 18 May 2026 (UTC)

Your assumption about the target of my question was correct, User:Malparti thanks for your help! I guess the only question have left is why <math>a ⫛ b</math> produces an error, and how to use ⫛ in math tag if so, but that's now irrelevant since I don't want to replace it anymore. Dingolover6969 (talk) 08:01, 21 May 2026 (UTC)

That's because you're mixing up two says to render math formula. There are to options for this:

• either use <math> </math>, in which case you have to use LaTeX markup -- so that would be <math>a \pitchfork b</math>, which gets rendered as $a\pitchfork b$. You can't use unicode in LaTeX code;
• or {{math| }}, in which case you have to use some other markup whose name I don't know. With that option, {{math|''a'' ⫛ ''b''}} gets rendered as a ⫛ b.

It's up to editors to chose which options to use. The second one has some advantages for accessibility, but LaTeX is more flexible and generally looks neater. It's also the default to write published math articles, so it is favored by most editors for somewhat advanced math. Malparti (talk) 08:09, 21 May 2026 (UTC)

Makes sense! Dingolover6969 (talk) 03:46, 22 May 2026 (UTC)

I no longer consider this "Dubious", because of the sources that User:Sławomir Biały found. I consider the matter fairly settled. If anyone happens to find a more authoritative source, like a textbook, that could also be useful, but there's no pressing need now. Dingolover6969 (talk) 08:01, 21 May 2026 (UTC)

"⋔" listed at Redirects for discussion

The redirect ⋔ has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at Wikipedia:Redirects for discussion/Log/2026 May 18 § ⋔ until a consensus is reached. Dingolover6969 (talk) 06:34, 18 May 2026 (UTC)