idiomatic
adj
(a) in accordance with the particular nature or structure of a language, dialect, etc 符合某一語言或方言等的習慣或特點的
She speaks fluent and idiomatic French. 她說得一口又流利又地道的法語.
(b) containing an idiom or idioms 含有習語的
an idiomatic expression, language 固定詞組、 成語多的語言.