Life partner, domestic partner, lover, boyfriend or girlfriend. Because gays and lesbians are not allowed to marry legally in the United States (although gay and lesbian marriages are allowed in some European countries), "significant other" is often equivalent to the term ispousei for lesbian, gay, bisexual and transgender people.

An individual's romantic partner.

SO Mate/partner, as in husband, wife, boy/girlfriend.

From the 1970s; a partner in a serious relationship. (RS)

One's chosen romantic partner.