weight class vs category

weight class and category both are nouns.

Word	Noun	Adjective	Verb	Adverb
weight class	Yes	No	No	No
category	Yes	No	No	No

As nouns, category is a hypernym of weight class; that is, category is a word with a broader meaning than weight class:

weight class: (combat sports) a division of competition used to match competitors against others of their own size.
category: a collection of things sharing a common attribute

Other hypernyms of weight class include class, family.

weight class (noun)	category (noun)
(combat sports) a division of competition used to match competitors against others of their own size.	a general concept that marks divisions or coordinations in a conceptual scheme
	a collection of things sharing a common attribute