significant other vs spouse equivalent

significant other and spouse equivalent both are nouns.

Word	Noun	Adjective	Verb	Adverb
significant other	Yes	No	No	No
spouse equivalent	Yes	No	No	No

As nouns, significant other and spouse equivalent are synonyms defined as:

significant other and spouse equivalent: a person (not necessarily a spouse) with whom you cohabit and share a long-term sexual relationship

Other synonyms of significant other include domestic partner, spousal equivalent.

significant other (noun)	spouse equivalent (noun)
a person (not necessarily a spouse) with whom you cohabit and share a long-term sexual relationship	a person (not necessarily a spouse) with whom you cohabit and share a long-term sexual relationship