II vs couple

II and couple both are nouns.

Word	Noun	Adjective	Verb	Adverb
II	Yes	No	No	No
couple	Yes	No	Yes	No

As nouns, couple is a hyponym of II; that is, couple is a word with a more specific, narrower meaning than II:

II: the cardinal number that is the sum of one and one or a numeral representing this number
couple: two items of the same kind

Other hyponyms of II include craps, snake eyes, brace, couplet, distich, duad, duet, duo, dyad, pair, span, twain, twosome, yoke.

II (noun)	couple (noun)
the cardinal number that is the sum of one and one or a numeral representing this number	a pair who associate with one another
	a pair of people who live together
	(physics) something joined by two equal and opposite forces that act along parallel lines
	two items of the same kind
	a small indefinite number

II (verb)	couple (verb)
	engage in sexual intercourse
	link together
	bring two objects, ideas, or people together
	form a pair or pairs