chain mail vs habergeon

chain mail and habergeon both are nouns.

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

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

chain mail: (Middle Ages) flexible armor made of interlinked metal rings
habergeon: (Middle Ages) a light sleeveless coat of chain mail worn under the hauberk

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

chain mail (noun)	habergeon (noun)
(Middle Ages) flexible armor made of interlinked metal rings	(Middle Ages) a light sleeveless coat of chain mail worn under the hauberk