id·i·om 
/ˈɪdijəm/ noun
plural id·i·oms /ˈɪdijəm/ noun 1 [count] : an expression that cannot be understood from the meanings of its separate words but that has a separate meaning of its own
▪ The expression “give way,” meaning “retreat,” is an idiom. 2 [count, noncount] : a form of a language that is spoken in a particular area and that uses some of its own words, grammar, and pronunciations : dialect 3 : a style or form of expression that is characteristic of a particular person, type of art, etc. [count] ▪ a poet's idiom ▪ rock and roll and other musical idioms [noncount] ▪ a feature of modern jazz idiom
▪ The expression “give way,” meaning “retreat,” is an idiom.
— id·i·om·at·ic /ˌɪdijəˈmætɪk/ adjective
▪ an idiomatic expression/phrase [=an expression/phrase that is an idiom] ▪ a use of language that is not idiomatic [=that does not sound natural or correct]
▪ an idiomatic expression/phrase [=an expression/phrase that is an idiom] ▪ a use of language that is not idiomatic [=that does not sound natural or correct]
— id·i·om·at·i·cal·ly /ˌɪdijəˈmætɪkli/ adverb
▪ That phrase is idiomatically acceptable/correct.
▪ That phrase is idiomatically acceptable/correct.
