chain armor vs chain armour

chain armor and chain armour both are nouns.

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

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

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

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

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