Synthetic topos theory
[0017] Definition

Let \(U\) be a universe, let \(I\) be a \(U\)-small category, and let \(X:I\rightarrow \mathord {\textnormal {\textsf {Topos}}}(U)\) be a functor. Suppose that \(X\) factors through the domain projection \(\mathord {\textnormal {\textsf {Etale}}}(Y)\rightarrow \mathord {\textnormal {\textsf {Topos}}}(U)\) for some \(U\)-topos \(Y\). By [0013] and [0014], the colimit of \(X\) exists. We call colimits obtained in this way étale colimits. Limits in \(\mathord {\textnormal {\textsf {Logos}}}(U)\) that are étale colimits in \(\mathord {\textnormal {\textsf {Topos}}}(U)\) are called étale limits.