In musical terminology, idiomatic refers to parts or pieces which are written both within the natural physical limitations of the instrument and human body and, less so or less often, the styles of playing used on specific instruments.

In linguistics, an idiom is an expression whose meaning does not follow from the meaning of the individual words of which it is composed.

In Spanish, the word idioma (= lengua) means language, and this is often reflected in their SL English—using idiom to refer to language.