  In a paper of 1974, Brian Day employed a notion of factorization system in
the context of enriched category theory, replacing the usual diagonal lifting
property with a corresponding criterion phrased in terms of hom-objects. We set
forth the basic theory of such enriched factorization systems. In particular,
we establish stability properties for enriched prefactorization systems, we
examine the relation of enriched to ordinary factorization systems, and we
provide general results for obtaining enriched factorizations by means of wide
(co)intersections. As a special case, we prove results on the existence of
enriched factorization systems involving enriched strong monomorphisms or
strong epimorphisms.
