sex act vs intercourse

sex act and intercourse both are nouns.

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

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

sex act and intercourse: 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)	intercourse (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
	communication between individuals