full plate armour vs full plate armor

full plate armour and full plate armor both are nouns.

Word	Noun	Adjective	Verb	Adverb
full plate armour	Yes	No	No	No
full plate armor	Yes	No	No	No

As nouns, full plate armour and full plate armor are synonyms defined as:

full plate armour and full plate armor: a historical type of personal armor made from iron or steel plates entirely encasing the wearer.

full plate armour (noun)	full plate armor (noun)
a historical type of personal armor made from iron or steel plates entirely encasing the wearer.	a historical type of personal armor made from iron or steel plates entirely encasing the wearer.