Idiom /(ĭd"ĭ*ŭm)/

Id·i·om

Idiom

n.
  1. The syntactical or structural form peculiar to any language; the genius or cast of a language.
    Idiom may be employed loosely and figuratively as a synonym of language or dialect, but in its proper sense it signifies the totality of the general rules of construction which characterize the syntax of a particular language and distinguish it from other tongues.
    — G. P. Marsh.
    By idiom is meant the use of words which is peculiar to a particular language.
    He followed their language [the Latin], but did not comply with the idiom of ours.
  2. An expression conforming or appropriate to the peculiar structural form of a language.
    Some that with care true eloquence shall teach, And to just idioms fix our doubtful speech.
  3. A combination of words having a meaning peculiar to itself and not predictable as a combination of the meanings of the individual words, but sanctioned by usage; as, an idiomatic expression; less commonly, a single word used in a peculiar sense.
    It is not by means of rules that such idioms as the following are made current: “I can make nothing of it.” “He treats his subject home.” Dryden. “It is that within us that makes for righteousness.” M. Arnold.
    Sometimes we identify the words with the object -- though by courtesy of idiom rather than in strict propriety of language.
  4. The phrase forms peculiar to a particular author; as, written in his own idiom.
    Every good writer has much idiom.
  5. Dialect; a variant form of a language.