If I am talking about my girl / woman, then if I'm married I can say simply "my wife". But if I'm not married what I can say?
Iv'e checked the definition for spouse, but it's for "a person's husband or wife". I understand that it's not for the one that a person live with without marriage.
Then I've checked the definition of "mate" and it's "UK informal word used as a friendly way of talking to someone, especially a man". In this word there are 2 problems: 1. it's informal. 2. it's mainly for women. It's not interchangeable between the genders.
Then I've checked the definition of "partner", and it's "the person you are married to or living with as if married to them, or the person you are having a sexual relationship with". So it seems that this the only formal one noun for referring to both genders while living without marriage ("living with as if married to them" as Cambridge says). Is that correct?