Relating to or conforming to the natural manner of expression in a language, often using phrases or expressions that are characteristic of a particular language.

Her idiomatic use of English made her sound like a native speaker.

Peculiar to or characteristic of a particular language or dialect.

The idiomatic expressions in his speech were difficult for non-native speakers to understand.

Containing or using a large number of idioms or set phrases.

The book is written in a highly idiomatic style.