Here is the idiom definition in one line: an idiom is a fixed group of words whose meaning cannot be worked out from the words one by one. "Spill the beans" has nothing to do with beans; it means to reveal a secret.
Native speakers use idioms without thinking, which is why they puzzle learners so much. The word idiom also has two wider senses, the natural way a language is spoken and the style of an art form, and this page covers all three.
Entry at a glance
Meaning
A set phrase with a meaning beyond its literal wordsPart of speech
Noun (plural: idioms)Pronunciation
ID-ee-uhmWord forms
idiomatic (adjective), idiomatically (adverb)Origin
Greek idioma, a peculiarity, from idios, one's ownExamples
break the ice, under the weather, piece of cakeRegister
Neutral; a grammar and language term
Idiom definition: three senses of the word
- A fixed expression (the main sense). A phrase like "hit the sack" (go to bed) or "cost an arm and a leg" (be very expensive). You cannot swap the words around and keep the meaning: "hit the bag" means nothing.
- The natural way a language works. The patterns that sound right to native speakers. "Make a decision" is English idiom; "do a decision" is not, though it is grammatically understandable.
- A style in art or music. The typical manner of a school or form: "he composed in a folk idiom," "the painter worked in a modern idiom."
The common thread is something peculiar to a particular language, group or style, which matches the Greek root meaning "one's own."
Examples, with what they really mean
| Idiom | Real meaning | In a sentence |
|---|---|---|
| under the weather | slightly ill | I'm a bit under the weather, so I'll work from home. |
| break the ice | ease tension when people first meet | The teacher started with a game to break the ice. |
| once in a blue moon | very rarely | My cousin calls once in a blue moon. |
| let the cat out of the bag | reveal a secret by accident | Dad let the cat out of the bag about the surprise trip. |
| bite the bullet | do something hard you have been avoiding | I finally bit the bullet and booked the dentist. |
| on the fence | undecided | She's still on the fence about changing colleges. |
How idioms behave in grammar
Idioms are mostly frozen. You can usually change the verb tense ("she spilled the beans") but not the key nouns ("she spilled the peas" loses the meaning). Some allow a little play, so "break the ice" can become "the ice was finally broken."
Many idioms are also informal. They fit conversation, emails to colleagues and stories, but formal reports and academic essays use them sparingly. The adjective idiomatic describes language that sounds natural: "Her English is fluent and idiomatic."
Idiom vs proverb, metaphor and cliche
- Proverb. A short saying that gives advice or a general truth, like "look before you leap." Many proverbs are idiomatic, but an idiom does not need to give advice.
- Metaphor. Describing one thing as another to make a point. Many idioms began as metaphors and then froze into fixed phrases.
- Cliche. An expression repeated so much that readers stop noticing it. A tired idiom can become a cliche.
- Phrasal verb. A verb plus a small word, like "give up" or "look after." Some phrasal verbs are idiomatic because their meaning is not obvious from the parts.
Where the word idiom comes from
Idiom reached English through French and Late Latin from the Greek idioma, meaning a peculiarity or a special phrasing, which comes from idios, "one's own, private." The same Greek root gives English idiosyncrasy, a habit peculiar to one person. So an idiom is, at heart, a way of speaking that belongs to one language and does not travel neatly into another.
Tips for learning idioms
- Learn each one inside a full sentence, not as a bare phrase.
- Note the tone: "kick the bucket" (to die) is jokey and would be hurtful at a funeral.
- Group them by theme, such as money, weather or the body.
- Do not translate them word for word between languages; each language has its own set.
- Notice how connotation and context change what a phrase suggests.
Want more words for describing language itself? Browse the grammar and writing collection.
Frequently asked questions
What is the definition of idiom in simple terms for students?
An idiom is a phrase that means something different from its words. For example, "it's raining cats and dogs" means it is raining very heavily.
How would you define idiom with an example?
"Piece of cake" is a classic one. It means something is very easy, as in "The quiz was a piece of cake."
Is an idiom a figure of speech?
Yes, idioms are usually counted as figurative language because their meaning is not literal. They are fixed, though, while a metaphor can be freshly invented.
How do you pronounce idiom?
ID-ee-uhm, with three short syllables. It is easy to confuse with idiot when spoken quickly, so stress the clear ee sound in the middle.
What does idiomatic mean?
Idiomatic means natural to native speakers, or full of idioms. An idiomatic translation sounds like real speech rather than a word-for-word copy.
Are idioms the same in every country?
No. British, American and Indian English share many idioms but each place also has its own, and other languages have entirely different sets.