What’s the difference between slang and idiom?


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[Tweet “An idiom is an expression whose meaning is different from the meanings of the individual words it contains.”]

An idiom is an expression whose meaning is different from the meanings of the individual words it contains.

For example, ‘couch’ means ‘sofa’ and ‘potato’ is a vegetable.


However, the idiom ‘couch potato’ means a ‘lazy person who watches a lot of TV’.

As you can see from the above example, it’s often quite difficult to guess what an idiom means.


Another example might be ‘once in a blue moon’ meaning ‘seldom, very rarely’. ‘Blue’ is a colour and the moon is the natural satellite that revolves around our planet – so it doesn’t really help you to understand this idiom if you’re only familiar with the meanings of the individual words.


Read more:

1000+ Most Popular English Idioms and Their Meanings

Difference between collocation, fixed expression and idioms?


[Tweet “Slang words are expressions that only certain groups of people use and understand.”]

On the other hand, slang words are expressions that only certain groups of people use and understand.

For example, teenagers use words that their parents don’t. Adults don’t use these words – either because they don’t understand them or because slang is not appropriate in a lot of contexts. Criminals, ethnic groups or even football fans might have their own slang expressions.


Slang words are often words that mean something else in everyday English. For example, ‘unreal’ normally means ‘not real’, however, as a slang word, used by young people, it means ‘fantastic, awesome’.


Have a look at our fantastic selection of idioms and slang words:

55 Most Commonly Used British and American Slang Words and Their Meanings

Teenage Slang Words by American, British and Australian Teens [Infographic]

Idioms and Slang words for Money



Thanks for your great answer Mel!

It may also be useful to add that ‘slang’ is commonly used in speech rather than writing, and is a very informal way of speaking to someone, so slang is generally used amongst friends or colleagues who have the same interests or backgrounds.

The majority of these terms relate to sex, drink, drugs, money, relationships and socialising. Although there are some old slang phrases, it is more common among the young people of today.

If you are going to use these, you should be very careful with how you use them and whom you use them with, as some people may find some terms quite offensive!

If I were you, I would not make a big effort to learn a lot of slang terms, as they can be very confusing and easily misconstrued, especially for English learners! It helps to have a basic understanding of them, but it may be best not to go out of your way to learn all of them.

The easiest way to describe idioms (or idiomatic expressions) is that they cannot be translated literally into another language, as they just wouldn’t make sense!

Most idioms are informal and are used in everyday speech, but there is also a wide range of formal idioms used in the business world.

Idioms are collocations or groups of words that can change from region to region. For example, one idiom may be used in Southern England but never heard of in the North of England, or an idiom might be really popular in one American state but disliked in another!

They also go in and out of fashion all the time, which makes them even harder to learn! The best way to learn idioms is through natural conversation with native speakers, as this would make it easier for you to hear how it can be used in context, and also when it is appropriate.

It helps to have a basic understanding of the most common idioms, but it is harder to learn them through self-teaching as there are no rules! Neither are they always grammatically correct nor decipherable with a dictionary! So make some English speaking friends and practise conversation with them – that would be the key to learning idioms.

Here are some useful links to help you make friends and practise your English:
Language Exchange Websites
Group Skype English Lessons
Practise English on Skype with Other Students
Practise English on WhatsApp with Other Students

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