informality vs manner

informality and manner both are nouns.

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

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

Other hypernyms of informality include personal manner.

informality (noun)	manner (noun)
a manner that does not take forms and ceremonies seriously	a way of acting or behaving
freedom from constraint or embarrassment	how something is done or how it happens
	a kind