chain mail vs gusset

chain mail and gusset both are nouns.

Word	Noun	Adjective	Verb	Adverb
chain mail	Yes	No	No	No
gusset	Yes	No	No	No

As nouns, gusset is a hyponym of chain mail; that is, gusset is a word with a more specific, narrower meaning than chain mail:

Other hyponyms of chain mail include brigandine, habergeon, byrnie, hauberk, voider.

chain mail (noun)	gusset (noun)
(Middle Ages) flexible armor made of interlinked metal rings	a piece of material used to strengthen or enlarge a garment
	a metal plate used to strengthen a joist
	a piece of chain mail covering a place unprotected by armor plate