[annzabelle]

I never took a real chem or bio class, but more than half my degree involved classes where 0 and ∅ were extremely frequently used. Thankfully no math or CS professor is stupid enough to use the letter o as a symbol or variable name.

[dieselgate]

Does ∅ relate to diameter, zero, or something else?

[dvdkon]

The empty set, I presume.

As a computer science student, I have to juggle O, o, 0, and ∅. (capital/lowercase letter, zero, empty set. Fun!