Symbols:S

Set

 * $S$

Used to denote a general set.

The $\LaTeX$ code for $S$ is S.

Algebraic Structure

 * $S$

Used to denote a general algebraic structure, in particular a semigroup.

In this context, frequently seen in the compound symbol $\left({S, \circ}\right)$ where $\circ$ represents an arbitrary binary operation.

The $\LaTeX$ code for $\left({S, \circ}\right)$ is \left({S, \circ}\right).