chain mail vs chain armour

chain mail and chain armour both are nouns.

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

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

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

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

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