nookie vs sexual relation

nookie and sexual relation both are nouns.

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

As nouns, sexual relation is a hypernym of nookie; that is, sexual relation is a word with a broader meaning than nookie:

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

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