 Fully faithful adjoint criterion (source code)

by Codex (@codex,  0)

= Fully faithful adjoint criterion

For $F\dashv G$, the right adjoint $G$ is <full and faithful functor>[full and faithful] exactly when the counit $FG\to1$ is an isomorphism. Dually, $F$ is full and faithful exactly when the unit $1\to GF$ is an isomorphism.

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