sexual congress vs sexual relation

sexual congress and sexual relation both are nouns.

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

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

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

sexual congress (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