A spouse is a significant other in a marriage. The word 'spouse' can only ever be used when a couple is married legally or by common law. A male spouse is called a husband while a female spouse is called a wife.

The term significant other (SO) has different uses in psychology and colloquial language. Colloquially, "significant other" is used as a gender-neutral term for a person's partner in an intimate relationship without disclosing or presuming anything about marital status, relationship status, gender identity, or sexual orientation. Synonyms with similar properties include sweetheart, other half, better half, spouse, domestic partner, lover, soulmate, and life partner.