Freyd general adjoint functor theorem (source code)

= Freyd general adjoint functor theorem
{c}

= General adjoint functor theorem
{synonym}

For a <functor> $U:\mathcal C\to\mathcal D$ between <locally small categories>, with $\mathcal C$ a <complete category>, $U$ has a <left adjoint> if and only if it preserves small <categorical limits> and satisfies the <solution-set condition>. The dual statement uses cocompleteness, small-colimit preservation and weakly terminal solution sets to characterize existence of a <right adjoint>.