Given a paradigm P which consists of values V1 ... Vn of a set of morphological categories; Vi and Vj are syncretic, and there is syncretism in P (between Vi and Vj), iff Vi and Vj are expressed by the same morph. Syncretism is also the diachronic process leading to syncretism in this sense, i.e. the merger of two values of a paradigm.

The concept of syncretism does not distinguish between homonymy and polysemy of Vi and Vj. The syncretic endings of the nominative and genitive singular in Latin turris ‘tower’ are homonymous; the syncretic nominative and accusative singular ending in Latin castrum ‘fort’ is polysemous.