manner vs demeanour

manner and demeanour both are nouns.

Word	Noun	Adjective	Verb	Adverb
manner	Yes	No	No	No
demeanour	Yes	No	No	No

As nouns, demeanour is a hypernym of manner; that is, demeanour is a word with a broader meaning than manner:

manner: a way of acting or behaving
demeanour: (behavioral attributes) the way a person behaves toward other people

Other hypernyms of manner include behavior, behaviour, conduct, demeanor, deportment.

manner (noun)	demeanour (noun)
a way of acting or behaving	(behavioral attributes) the way a person behaves toward other people
how something is done or how it happens
a kind