manner vs idiom

manner and idiom both are nouns.

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

As nouns, idiom is a hyponym of manner; that is, idiom is a word with a more specific, narrower meaning than manner:

manner (noun)	idiom (noun)
a way of acting or behaving	the style of a particular artist or school or movement
how something is done or how it happens	the usage or vocabulary that is characteristic of a specific group of people
a kind	an expression whose meanings cannot be inferred from the meanings of the words that make it up
	a manner of speaking that is natural to native speakers of a language