Definition 1.1.0.6. Let $\operatorname{Set}$ denote the category of sets. A simplicial set is a simplicial object of $\operatorname{Set}$: that is, a functor $\operatorname{{\bf \Delta }}^{\operatorname{op}} \rightarrow \operatorname{Set}$.
$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$