Idiom

An idiom is an expression (i.e., term or phrase) whose meaning cannot be deduced from the literal definitions and the arrangement of its parts, but refers instead to a figurative meaning that is known only through common use. In linguistics, idioms are widely assumed to be figures of speech that contradict the principle of compositionality; however, some debate has recently arisen on this subject.

In the English language expression to kick the bucket, for example, a listener knowing only the meaning of kick and bucket would be unable to deduce the expression's actual meaning, which is to die. Although it can refer literally to the act of striking a specific bucket with a foot, native speakers rarely use it that way. It cannot be directly translated to other languages – for example, the same expression in Polish is to kick the calendar, with the calendar being as detached from its usual meaning as the bucket in the English phrase is. The same expression in Dutch is het loodje leggen (to lay the piece of lead), which is entirely different from the English expression, too. Other expressions include break a leg, crossing the Rubicon and fit as a fiddle. It is estimated that William Shakespeare coined over 2,000 idioms still in use today.

Idioms hence tend to confuse those not already familiar with them; students of a new language must learn its idiomatic expressions the way they learn its other vocabulary. In fact many natural language words have idiomatic origins, but have been sufficiently assimilated so that their figurative senses have been lost.