servicing vs sexual union

servicing and sexual union both are nouns.

Word	Noun	Adjective	Verb	Adverb
servicing	Yes	No	No	No
sexual union	Yes	No	No	No

As nouns, sexual union is a hypernym of servicing; that is, sexual union is a word with a broader meaning than servicing:

servicing: the act of mating by male animals
sexual union: the act of pairing a male and female for reproductive purposes

Other hypernyms of servicing include conjugation, coupling, mating, pairing, union.

servicing (noun)	sexual union (noun)
the act of mating by male animals	the act of pairing a male and female for reproductive purposes