manner vs demeanor

manner and demeanor both are nouns.

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

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

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

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

manner (noun)	demeanor (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