DINK vs mates

DINK and mates both are nouns.

Word	Noun	Adjective	Verb	Adverb
DINK	Yes	No	No	No
mates	Yes	No	No	No

As nouns, mates is a hypernym of DINK; that is, mates is a word with a broader meaning than DINK:

DINK: a couple who both have careers and no children (an acronym for dual income no kids)
mates: a pair of people who live together

Other hypernyms of DINK include couple, match.

DINK (noun)	mates (noun)
a couple who both have careers and no children (an acronym for dual income no kids)	a pair of people who live together