sexual cardinality

Sexual Cardinality (Cardinality from set theory) is a word for the trait defining a person's numerical preference of romantic partners.

Sexual Cardinality is to {polyamorous, monogamous, asexual/aromantic} as Sexual Orientation is to {straight/gay/bisexual}

"What's your sexual orientation and sexual cardinality?"

Oh, I'm mostly straight and strictly polyamorous" or "I'm bisexual and monogamous"