chain armour vs byrnie

chain armour and byrnie both are nouns.

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

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

chain armour: (Middle Ages) flexible armor made of interlinked metal rings
byrnie: a long (usually sleeveless) tunic of chain mail formerly worn as defensive armor

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

chain armour (noun)	byrnie (noun)
(Middle Ages) flexible armor made of interlinked metal rings	a long (usually sleeveless) tunic of chain mail formerly worn as defensive armor