chain armor vs chain mail

chain armor and chain mail both are nouns.

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

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

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

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

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