[DarylZero]

Also I just want to add... mathematicians have ⋅, ×, and ∗ to express multiplication, but decided that they also needed ADJACENCY OF CHARACTERS to express multiplication, and therefore mathematics is not allowed to use variable names longer than one letter.

Come the fuck on, mathematics.

[kmill]

It's fine, you just add a space. It's also used for function application, like "sin x".

I'd say single-letter variable names are mostly due to ease of handwriting when doing calculations (or for giving a chalkboard talk), and authors tend to just use what they've already come up with when writing things up. Mathematicians seem to be very tolerant of ambiguous parsing, so that can't explain all of it.

[sieste]

When reading a math proof it helps to spell out what the symbols stand for, instead of saying the symbol names, for example, instead of "E equals m c squared" say "energy equals mass times speed of light squared". This also greatly helps understanding. If you can't keep track because there are too many symbols, make a little lookup table.

[DarylZero]

You can point to "sin", but in practice math just doesn't use multi-char variable names. The trig functions are special cases. Doesn't mean you're allowed to name arbitrary vars like that.

[kmill]

What about ker, coker, im, hom, end, aut, lim, colim, Set, Top, Man, Mat, Vect, GL, SL, SO, Lie, Gr, Tor, Ext, tr, Rep, char, rank, Isom, ann, hull, Diff, ...? I'm just copying multiletter names out of my preamble.tex file here.

I get that these aren't variables, but it's really not so uncommon outside of trigonometry to have multi-letter names for things that appear in equations.