couple vs mismate

couple is a noun but mismate is not a noun.

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

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

Other hyponyms of couple include mismatch.

couple (noun)	mismate (noun)
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

couple (verb)	mismate (verb)
engage in sexual intercourse	provide with an unsuitable mate
link together
bring two objects, ideas, or people together
form a pair or pairs