Today I Learned

Some of the things I've learned every day since Oct 10, 2016

79: Hom-Set

In category theory, the hom-set between 2 objects $X, Y$ in a category $C$, often denoted as

$\textrm{hom}_C (X, Y)$

or simply

$\textrm{hom} (X, Y)$

is the collection of arrows (morphisms) in $C$ from $X$ to $Y$. Note that despite the name, the hom-set is not a set in general.