I am usually writing LaTeX documents. I like to use
:iab iso isomorphism
so that if I write a sentence like
This map is an iso., it will expand to
This map is an isomorphism.. However, I also quite frequently use the command
\iso in math mode. So for example, I will write
$f \colon V \iso W$ and nothing should be expanded. In other words, the backslash should be counted like a regular character at the beginning of the word, just as
aiso would not be expanded.