What is the place holder glyph for a set?

Question

What glyph do set theorists use to denote an unspecified set?

For example, logicians use φ to talk about an unspecified sentence in first order logic. Does set theory have a comparable glyph?

Thank you.

Answer 1

Technically you can name a set anything you want, but some names are more conventional than others. In my experience, mathematicians often use capital letters in the upper part of the English alphabet -- $A$, $B$, $C$, etc. -- to name sets, at least in elementary treatments. A good way to determine the "standard" notational convention for something like a set is to find books or articles which use sets in the same context as you. The context is important because almost every mathematical object is a set: "$1$" is the name of a set, for example, although you would confuse everyone greatly if you wrote "let $1$ be a set . . ."