chain armour vs gusset

chain armour and gusset both are nouns.

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

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

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

chain armour (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