ring mail vs byrnie

ring mail and byrnie both are nouns.

Word	Noun	Adjective	Verb	Adverb
ring mail	Yes	No	No	No
byrnie	Yes	No	No	No

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

ring mail: (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 ring mail include brigandine, habergeon, hauberk, gusset, voider.

ring mail (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