Calligraphic

Synopsis:

\mathcal{uppercase-letters}

Use a script-like font.

In this example the graph identifier is output in a cursive font.

Let the graph be \( \mathcal{G} \).

If you use something other than an uppercase letter then you do not get an error but you also do not get math calligraphic output. For instance, \mathcal{g} outputs a close curly brace symbol.