cohabitation

This term carries a neutral to clinical tone, often appearing in legal, sociological, or biological documents. In a social context, it describes a specific domestic arrangement that avoids the formal constraints of marriage, focusing on the shared physical space and daily routine of a couple.

In biological or ecological contexts, the word shifts toward a descriptive observation of coexistence. It emphasizes the spatial overlap of different organisms within a single environment, regardless of whether their interaction is symbiotic or competitive.