carnal knowledge vs sexual relation

carnal knowledge and sexual relation both are nouns.

Word	Noun	Adjective	Verb	Adverb
carnal knowledge	Yes	No	No	No
sexual relation	Yes	No	No	No

As nouns, carnal knowledge and sexual relation are synonyms defined as:

carnal knowledge 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

Other synonyms of carnal knowledge include coition, coitus, copulation, intercourse, relation, sex act, sexual congress, sexual intercourse.

carnal knowledge (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