idiomatic
adj
(a) in accordance with the particular nature or structure of a language, dialect, etc 符合某一语言或方言等的习惯或特点的
She speaks fluent and idiomatic French. 她说得一口又流利又地道的法语.
(b) containing an idiom or idioms 含有习语的
an idiomatic expression, language 固定词组、 成语多的语言.