coitus vs sexual relation

coitus and sexual relation both are nouns.

Word	Noun	Adjective	Verb	Adverb
coitus	Yes	No	No	No
sexual relation	Yes	No	No	No

As nouns, coitus and sexual relation are synonyms defined as:

coitus and sexual relation: sexual activity between individuals, especially the insertion of a man's penis into a woman's vagina until orgasm and ejaculation occur

coitus (noun)	sexual relation (noun)
sexual activity between individuals, especially the insertion of a man's penis into a woman's vagina until orgasm and ejaculation occur	sexual activity between individuals, especially the insertion of a man's penis into a woman's vagina until orgasm and ejaculation occur