Someone who is monogamous or who has a monogamous relationship has a sexual relationship with only one partner. Do you believe that men are not naturally monogamous?
Monogamy is the state or custom of being married to only one person at a particular time. In many non-Western societies, however, monogamy has never dominated
[ -mE ] (noun.) 1612. French monogamie, from Late Latin monogamia, from Greek, from monogamos monogamous, from mon- + gamos marriage, from gamein to marry.