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What is the difference between an expression and a phrase?
Difference between “phrase” and “idiom”

What is the difference between a phrase, an idiom and an expression? I am looking for the context where one is more appropriate than the rest. I've been using idiom and phrase more or less interchangeably.

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    Related-expression vs phrase: english.stackexchange.com/questions/8905/… Phrase vs idiom(linked below too) english.stackexchange.com/questions/16343/… Commented Aug 27, 2011 at 23:06
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    @Bogdan: Is there a problem with dr65s answer?
    – user10893
    Commented Aug 30, 2011 at 3:49
  • @simchona Thank you for your concern 1.It is no mandatory to justify a bounty. One can use the imagination. Quoting the faq, bounties are "to get better answers". Note also that "If you do not award your bounty within 7 days, the highest voted answer created after the bounty started with at least 2 upvotes will be awarded half the bounty amount." 2.I do not believe that the best answers are Platonic ideal forms. And this means answers can be given from a different perspective. Commented Aug 30, 2011 at 6:24
  • @Bogdan Yes, bounties are to "get better answers". Perhaps it might be helpful to state how you think the given/accepted answer might be improved? If not, this will turn into a citing of various definitions in an attempt to gain the prize.
    – user10893
    Commented Aug 30, 2011 at 6:55

3 Answers 3


This question asks nearly the same thing.

This is the difference between an idiom and a phrase:

A phrase is “a small group of words standing together as a conceptual unit”, while an idiom is “a group of words established by usage as having a meaning not deducible from those of the individual words”. So, the difference is that an idiom as an established meaning not directly linked to the individual words. Any idiom is a phrase.

As an example, “raining cats and dogs” is both an idiom and a phrase. “A herd of cats” is a phrase but not an idiom.

Expression has about the same meaning as phrase, except it is usually used of a phrase which is in common use.

So an idiom is a certain sort of expression, which in turn is a subset of phrase: idiom > expression > phrase.


An idiom can be a single word, if it's used in a way that isn't its literal or dictionary meaning. For example, "moonlighting" to mean having a second job is an idiom. A phrase is any clump of words ( "that dog over there", "my cousin's wife's sister", "because it was hot", "as fast as I can"), and an expression is a phrase that is an idiom.

So: all expressions are phrases, and all expressions are idioms. But some phrases are not expressions, and some idioms are not phrases or expressions.

Further, "just because you say it doesn't make it a saying": opinions may vary on whether a particular phrase is an expression or not.


This question was a subset of the question asked above by @Fedor. However, the answer provides a good framework for answering the current question too.

We have three terms here: expression, idiom and phrase.

An expression is a saying. It may be a colloquial, less formal (or more polite) way of expressing something in less literal terms:

How do you do? is an expression. You don't expect someone to actually tell you how he is doing; he should just say How do you do? because it means little more than "hello" [2]

A phrase is a semantically meaningful sequence of words. A phrase is not typically a complete sentence. I consider a phrase to be more like a grammatical construct e.g.

  • needless to say
  • causing permanent bodily harm
  • way of the world

Idiom is more subtle. It can be informal or merely non-literal, and either a phrase or a complete sentence. Here are two examples of idioms that are also phrases:

  • brick and mortar (a traditional business, in contrast to e-commerce)
  • town and gown (when a school or university is in close proximity with a surrounding community, this is a way of distinguishing between academicians or students versus local residents who are not affiliated with the school)

Here's the subtle part: It requires an idiomatic understanding of language to use these non-obvious forms of speech correctly. Idioms resemble metaphors, but are more general.

  • Here's my take. You wrote here idiomatic phrases and expressions(ex. needless to say is not “random”), which do not necessarily equal idioms but they have an idiomatic, common usage touch. These are also called phrasal idioms, idiomatic/common expressions, set phrase, etc. And they have subtle meanings, given by you, which however can be obscured in common language. Commented Aug 31, 2011 at 23:57
  • In addition to that, phrase and expression have additional strictly grammatical meanings. So that a phrase consists of typical two or more words (what Kate Gregory mentions). A phrase can be a sentence but usually is not. An expression is the more general case and can be a word, phrase or sentence Commented Aug 31, 2011 at 23:57
  • So at the end, actually "idiom" has the clearest definition (established meaning not directly linked to the individual words). Commented Sep 1, 2011 at 0:03
  • First, I want to thank you @Bogdan for emphasizing this question. I tried to do what others did, and classify the three terms using a transitive relationship. Not quite that simple. The more I thought about this, the closer I got to erasing my entire answer and giving up! In response to your fine comments: I did not say that phrases (such as "needless to say") were random combinations of words, not semantically linked. But I remember reading that on ESL yesterday, yet can't find it now! Kate Gregory conveyed better what I meant re categorizing phrase vs expression as sentence or fragment. Commented Sep 1, 2011 at 14:56
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    Please don't erase it-note that this question had a bounty from me and you got it. I didn't say your phrase was random, on the contrary, I wanted to emphasize that it is not. So from your comment I see that you wanted to say the same thing about phrase as Kate Gregory(I misunderstood before that you diverged on that point). So now I see what you meant by semantical (which is the same as what I meant by grammatical). But note phrase could in addition mean idiomatic phrase. So there are two meanings of "phrase" and "expression". Commented Sep 1, 2011 at 19:32

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