What Is an Idiom? Phrases Whose Meaning Is Not in the Words
By the BrainSnail editorial team. How these articles are written and checked, and how to tell us when one is wrong.
Kick the bucket means to die, and no amount of knowledge about kicking or about buckets will get you there. That is the defining property: an idiom's meaning cannot be worked out from its parts, which makes it invisible to a learner who knows every word in it and a persistent difficulty for translation. Every language has thousands of them, and the estimates suggest a fluent speaker knows tens of thousands of such fixed expressions.
What makes a phrase idiomatic
Several properties distinguish an idiom from an ordinary phrase, and most idioms have all of them:
- •Non-compositionality, meaning the whole does not follow from the parts, which is the defining feature
- •Fixed form, so that substituting a synonym breaks it, since spill the beans works and tip the beans or spill the peas do not
- •Grammatical resistance, since many idioms cannot be passivised, questioned or modified: he kicked the bucket works and the bucket was kicked by him does not carry the meaning
- •Conventionality, since the phrase must be established in a community rather than invented on the spot
- •Degrees of transparency, running from opaque expressions whose origin nobody can reconstruct, through ones where the metaphor is visible once pointed out, to near-literal ones
- •A related family of fixed expressions, including collocations where words simply prefer each other, so that tea is strong and rain is heavy for no reason a learner can derive
How the brain handles them
Psycholinguistic research has found that idioms are processed faster than equivalent literal phrases, which is the opposite of what a model requiring literal interpretation followed by rejection would predict. The explanation now favoured is that a familiar idiom is stored and retrieved as a unit, in something like the way a single long word is, so that recognition begins before the phrase is complete and the ending is highly predictable. That storage has consequences: idioms survive in the speech of people with some aphasias after ordinary sentence construction has failed, which suggests a different retrieval route. Figurative meaning nonetheless remains connected to the literal image for many speakers, demonstrated by the finding that idioms whose underlying metaphor is still visible behave differently from opaque ones in comprehension tasks, and that speakers can extend a live metaphor while an opaque idiom resists any variation at all.
Where they come from
Origins divide into ones that are documented and ones that are invented afterwards. Documented sources include trades and technologies, so that a great many English idioms come from sailing, from weaving, from printing and from archery, and their opacity increases as the practice disappears; horse trading, blacksmithing and the mechanics of a sailing ship supply an enormous proportion of the fixed expressions in English. Literature and scripture contribute heavily, with Shakespeare and the King James Bible between them supplying a large share of common English idioms. Historical incidents supply a few. What is far more common than any of these is the folk etymology, an appealing story attached to a phrase after the fact and repeated until it is believed, and the reliable indicator is a story that is specific, vivid and involves a colourful historical practice. Lexicographers treat such accounts sceptically by default and the honest entry for a great many idioms records the earliest attestation and states that the origin is unknown.
The translation problem
Idioms are among the hardest things to translate and the strategies are limited. A translator can find an equivalent idiom in the target language, which preserves the register and changes the image, so that an English expression about raining cats and dogs becomes a French one about ropes. They can translate the sense plainly, which preserves the meaning and loses the colour. They can translate literally and add an explanation, which is accurate and clumsy. Or they can substitute an idiom with a similar image where one happens to exist. The problem is worse where the idiom is doing work in the text, since a pun on an idiom or a passage that revives its literal meaning cannot be handled by any of these. Machine translation has improved substantially here because modern systems work on sequences rather than words and have seen the phrases in training, which is why current output handles common idioms well and still fails on rare ones, on newly coined ones and on any passage where the literal and figurative senses are both live.
The takeaway
An idiom's meaning cannot be derived from its words, its form is fixed so that synonyms break it, and it resists the grammatical operations ordinary phrases allow. Familiar idioms are stored and retrieved as units, which is why they are processed faster than literal equivalents and survive in some kinds of language impairment. Many come from obsolete trades, from scripture and from literature, and a great many circulating origin stories are invented after the fact. Translation must choose between preserving the image, the sense or the register.