1. A speech form or an expression of a given language that is peculiar to itself grammatically or cannot be understood from the individual meanings of its elements, as in keep tabs on.
2. The specific grammatical, syntactic, and structural character of a given language.
3. Regional speech or dialect.
4. A specialized vocabulary used by a group of people; jargon: legal idiom.
5. A style of artistic expression characteristic of a particular individual, school, period, or medium: the idiom of the French impressionists; the punk rock idiom.
[Late Latin idiōma, idiōmat-, from Greek, from idiousthai, to make one's own, from idios, own, personal, private; see s(w)e- in the Appendix of Indo-European roots.]
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