spouse vs domestic partner

spouse and domestic partner both are nouns.

Word	Noun	Adjective	Verb	Adverb
spouse	Yes	No	No	No
domestic partner	Yes	No	No	No

As nouns, domestic partner is a hypernym of spouse; that is, domestic partner is a word with a broader meaning than spouse:

spouse: a person's partner in marriage
domestic partner: a person (not necessarily a spouse) with whom you cohabit and share a long-term sexual relationship

Other hypernyms of spouse include significant other, spousal equivalent, spouse equivalent, relation, relative.

spouse (noun)	domestic partner (noun)
a person's partner in marriage	a person (not necessarily a spouse) with whom you cohabit and share a long-term sexual relationship