kg vs metric weight unit

kg and metric weight unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
kg	Yes	No	No	No
metric weight unit	Yes	No	No	No

As nouns, metric weight unit is a hypernym of kg; that is, metric weight unit is a word with a broader meaning than kg:

kg: one thousand grams; the basic unit of mass adopted under the Systeme International d'Unites
metric weight unit: a decimal unit of weight based on the gram

Other hypernyms of kg include weight unit.

kg (noun)	metric weight unit (noun)
one thousand grams; the basic unit of mass adopted under the Systeme International d'Unites	a decimal unit of weight based on the gram