ring armour vs ring mail

ring armour and ring mail both are nouns.

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

As nouns, ring armour and ring mail are synonyms defined as:

ring armour and ring mail: (Middle Ages) flexible armor made of interlinked metal rings

Other synonyms of ring armour include chain armor, chain armour, chain mail, mail, ring armor.

ring armour (noun)	ring mail (noun)
(Middle Ages) flexible armor made of interlinked metal rings	(Middle Ages) flexible armor made of interlinked metal rings