Distance to semicolon in math mode

Question

When using colon (:) in math mode, it always appears equidistant from the objects on either side of it.

Observe this e.g. when typesetting $(a:b)$ .

If one instead uses $(a \colon b)$ , the colon is closer to the a, as it would be in ordinary writing.

On the other hand, if one typesets $(a;b)$ , one finds that the semicolon is not equidistant between a and b, but closer to the a, as with the \colon command above.

So my question is: Is there a command that creates a semicolon equidistant from the objects to either side of it, as with the :?

Use $(a \mathbin{;} b)$ ... – Thruston Apr 09 '20 at 07:34 — Thruston, Apr 09 '20 at 07:34
See also: https://tex.stackexchange.com/q/427799/15036 – Thruston Apr 09 '20 at 07:37 — Thruston, Apr 09 '20 at 07:37

score 4 · Accepted Answer · answered Apr 09 '20 at 07:45

LaTeX inherits a set of plain TeX commands that let you change the "class" of each character in math mode. The various classes determine how the TeX engine inserts white space in a formula.

There are 8 classes:

0 = Ordinary \
1 = Large operator \sum
2 = Binary operator +
3 = Relation =
4 = Opening (
5 = Closing )
6 = Punctuation ,
7 = Variable

I think ; is punctuation by default, but you can make it behave like a binary operator with \mathbin{;} or like a relation with \mathrel{;}.

The corresponding commands for the first 7 classes are: \mathord, \mathop, \mathbin, \mathrel, \mathopen, \mathclose, and \mathpunct.

See the TexBook, p.155 for more.

Distance to semicolon in math mode

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