Idioms
[Idioms definition from Wikipedia, the free encyclopedia -
www.en.wikipedia.com]
An idiom is an expression (ie. term or phrase) whose meaning cannot be deduced from a literal definition of its parts, and instead refers to a nonliteral or figurative meaning which is only known through conventional use. In linguistics, idioms are constructs of natural language which contradict the principle of compositionality which more formal languages follow. They are typically classified as figures of speech.
For example, the English phrase
to kick the bucket means
to die. A listener knowing only the meaning of kick and bucket would not be able to deduce what the expression actually means. Though the phrase wikt:to kick the bucket can literally refer to the act of giving a kick to a bucket, (and is thought to refer to how livestock kicked a buque (French) when slaughtered[1]), the literal interpretation is a rarity when native speakers use the phrase, and students of a new language can often be frustrated by their use.
The term "idiom" hence tends to refer to groups of words which are overtly confusing to those not familiar with the term. However many terms from natural language are in fact idioms or have idiomatic origin, but have been assimilated into the language such that the original idiom has been lost.