S: (n) coupling, mating, pairing, conjugation, union, sexual union (the act of pairing a male and female for reproductive purposes) "the casual couplings of adolescents"; "the mating of some species occurs only in the spring"
S: (n) union, unification, uniting, conjugation, jointure (the act of making or becoming a single unit) "the union of opposing factions"; "he looked forward to the unification of his family for the holidays"