Into a syncretism may enter, besides explicit entities, the zero entity, which has a quite special significance for linguistic analysis. The necessity has often been noted of recognizing the existence of ‘latent’ and ‘facultative’ linguistic entities, especially “phonemes” [...] A moment’s reflexion is enough to show that latency and facultativity cannot be defined as suspended manifestation; the functions in question are grounded in the linguistic schema, since the conditions under which latency and facultativity appear are fixed by relations in the chain and rest on dominance. Latency and facultativity must then be understood as overlapping with zero. ‘Latency’ is an overlapping with zero in which the dominance is obligatory (since the dominant in respect to the syncretism is a variety), and a functive that contracts latency is called ‘latent’.
- Hjelmslev (1961), a pag.93