boxer vs featherweight

boxer and featherweight both are nouns.

Word	Noun	Adjective	Verb	Adverb
boxer	Yes	No	No	No
featherweight	Yes	No	No	No

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

boxer (noun)	featherweight (noun)
a breed of stocky medium-sized short-haired dog with a brindled coat and square-jawed muzzle developed in Germany	A weight class division in combat sports, for fighters heavier than those in the bantamweight division and lighter than those in the lightweight division.
someone who fights with his fists for sport	a professional boxer who weighs between 123 and 126 pounds
a workman employed to pack things into containers	weighs 126-139 pounds
	an amateur boxer who weighs no more than 126 pounds