significant other vs spousal equivalent

significant other and spousal equivalent both are nouns.

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

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

significant other and spousal 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, spouse equivalent.

significant other (noun)	spousal 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