sex act vs coitus

sex act and coitus both are nouns.

Word	Noun	Adjective	Verb	Adverb
sex act	Yes	No	No	No
coitus	Yes	No	No	No

As nouns, sex act and coitus are synonyms defined as:

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

sex act (noun)	coitus (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