de facto wife; common-law wife
A woman who lives with a man in a marriage-like relationship without legal registration. The term is used in legal and social contexts, often in contrast to a legally married wife (法律上の妻).
He has been living with his common-law wife for over ten years.
A de facto wife may not be granted inheritance rights in some cases.
Refers to the broader concept of a de facto marriage, while 内縁の妻 specifically denotes the female partner in such a relationship.
Compound of 内縁 (ないえん, 'private relationship' or 'de facto marital relation') and 妻 (つま, 'wife'). The term is a modern legal and social expression.