behaviour vs demeanor

behaviour and demeanor both are nouns.

Word	Noun	Adjective	Verb	Adverb
behaviour	Yes	No	No	No
demeanor	Yes	No	No	No

As nouns, behaviour and demeanor are synonyms defined as:

behaviour and demeanor: (behavioral attributes) the way a person behaves toward other people

Other synonyms of behaviour include behavior, conduct, demeanour, deportment.

behaviour (noun)	demeanor (noun)
manner of acting or controlling yourself	(behavioral attributes) the way a person behaves toward other people
(psychology) the aggregate of the responses or reactions or movements made by an organism in any situation
(behavioral attributes) the way a person behaves toward other people
the action or reaction of something (as a machine or substance) under specified circumstances