During your IELTS preparation, you might hear people talking about formal and informal vocabulary. In fact, the matter of formal vs informal goes beyond just vocabulary and encompasses other parts of language: grammar, punctuation, structure, etc.

In today’s lesson, I want to explain to you what is meant by formal and informal language, and clearly show you what you need to do for your IELTS exam. This article is going to focus on IELTS writing because this is the most important part of the test relating to this topic.

What do we mean by formal and informal language?

When you first learn English, you are just learning a language. You probably don’t think much about different types of English. However, there are different versions of most languages, and often this revolves around the idea of polite vs casual speech.

In some countries, like Japan or Korea, it is very important to choose the correct form of language when speaking with someone else, or you might cause serious offense. English speaking countries tend to be quite modern and liberal, so you won’t cause much offense if you speak to someone in an informal manner. However, it is still important to make an effort.

Formal language is generally used in business, education, and for most serious matters. Informal language is more appropriate for friends, but it appears to be spreading into the wider world.

When it comes to IELTS, you are being tested in terms of specific English skills. For the academic test, you need to know very basic academic practices, and for the general test you need to know more informal approaches.

What is the Difference Between Formal and Informal Language?

There are many differences between formal and informal language and you really don’t need to know them all. However, I would recommend studying some of the most common features, as misusing these could prove costly.

Here are a few differences:

Features of Formal WritingFeatures of Informal Writing
No (or few) contractionsContractions
Some use of passive voiceLittle use of passive voice
No slangSome slang
Structures like participle clausesStraightforward language
Mostly correct grammarLots of “lazy” grammar
Few personal pronounsMore personal pronouns
Occasional idiomsFrequent idioms
Proper transition wordsCasual transitions

Formal Language for IELTS

When it comes to IELTS, formal language is most important for the writing test. In the academic exam, you will need to write both task 1 and task 2 essays in formal language, but for general training you may only have to put task 2 into formal language. Task 1 may be formal, semi-formal, or informal, depending on the requirements. (We’ll return to that later.)

To write formally, you need to think of a few things:

  • You should use accurate vocabulary that provides precise meanings and does not impart too much subjective opinion.
  • It is best to avoid slang, colloquialisms, and other such informal vocabulary.
  • You must aim to use grammar in a conventional sense.

A lot of IELTS students think that they must use ridiculously complicated vocabulary, but this is not true. Formal vocabulary does tend to be a little more advanced and complicated, but it is not the same as looking up obscure words in a dictionary. (Please avoid any teacher that tells you, “Use these magic words to get a band 8!”)

As for grammar, you should aim to use proper grammar, but do not think you must use the most complicated structures possible. Yes, long sentences are a feature of academic language, but you do not need to do this. Just being accurate is best.

Formal Vocabulary for IELTS

Firstly, there is no such thing as formal vocabulary for IELTS. There is informal vocabulary and there is correct vocabulary. When you write essays for academic IELTS, you should not try to think, “What is the most formal word for this situation?” This sort of thought process will lead you to make mistakes.

Instead, always aim for the most accurate word. This is of the utmost importance. If you use a word that is correct, you will not be penalised unless it is also extremely informal. For example, imagine that you want to talk about the environment and you decide to talk about cutting down trees. Well, the word we use for this phenomenon is “deforestation.” It is a good word and appropriate for the context. Some might even call it a formal or advanced word.

Considering that, which of these sentences is better:

  1. Over the past fifty years, human beings have cut down more than half of the world’s trees.
  2. Over the past fifty years, human beings have deforestation more than half of the world’s trees.

The correct answer is #1 because this is grammatically correct. The word “deforestation” is a noun that refers to the idea of cutting down trees. We can use it as a verb in some very limited cases, but not here.

Remember: The most important thing about vocabulary for IELTS is using it accurately.

Formal Grammar for IELTS

I am hesitant to encourage the use of “advanced grammar” or anything like that because it’s not really worthwhile. As I said before, using correct and precise language is the most important thing. However, I will mention a few features of formal English grammar:

  • The passive voice is more common in formal writing than informal writing. This is because it tends to be more factual and objective than informal writing, and allows for the removal of some personal elements. However, do not overdo it. Any essay with too much passive voice immediately sounds bad.
  • Participle clauses are a feature of formal and classical language. These can help you to sound a little more authoritative and show a certain mastery of style, but using them too often is a big problem. Even used twice in a sentence, these can be quite awkward.

Informal Language for IELTS

Ok, next we will talk about informal language. This is probably more useful because “formal language” covers most of what we actually use in written English.

Informal language is often known as “casual” or “colloquial” language. It basically means that was is not formal, and it used to be considered very rude. Nowadays, however, it is perfectly normal, but we still should avoid it in written English.

Informal language involves omitting words, shortening words, and using words creatively, inaccurately, or carelessly. It could also include swearing, but we will not cover that because it is not advisable for IELTS.

Informal Language for IELTS Writing

First of all, let’s briefly look at IELTS writing and how informal language may possibly be used. For most essays, it is best avoided. You should use the abovementioned formal structures instead.

However, if you are doing IELTS general training and you need to write a letter to someone that you know well socially or as a family member, then you can use informal language.

Features of Informal Language

Informal language can include slang and other colloquialisms. We may also use personal pronouns, idioms, and contractions. It is also occasionally possible to break the rules of grammar, such as in this example:

  • Hope to hear from you soon!

In this case, I have dropped the subject (“I”) and begun the sentence with a verb. This is normally considered bad grammar, but in informal writing we sometimes do this.

Informal LanguageExplanationExample
SlangCasual, informal, or modern words that are not part of standard English.“I want to know if you’re down to hit the cinema this weekend.” (down to = willing; hit = go to)
Personal pronounsWords like “I,” “we,” etc.“We really should get together soon.”
ContractionsShortening words or bringing two words together into one.“They’re going to give us their old furniture. Isn’t that nice?” (they’re = they are; isn’t = is not)
IdiomsPhrases that have a different meaning from their individual parts.“It was really a blessing in disguise to see her at the store.” (blessing in disguise = a surprisingly good thing)

All of this should be avoided for essays, but it is acceptable when you are writing a letter to a friend or family member.

Informal Letters

The only place in the IELTS writing test where you should have a good grasp of informal language is the letter section of the general exam. Here, if you think it is appropriate, you can include some of the above ideas. Let’s look at a sample answer:


You recently visited a place that had a strong impact on you. Write a letter to a friend about the place. In your letter

  • explain where the place was and how you got there
  • describe what you saw
  • offer to take your friend there

Sample Answer

Hello Simon,

I just got back from Big Sur, where I spent two weeks camping in the mountains. It was an amazing trip and, as you had said you were interested, I thought I’d write and tell you about it.

I slept in a tent most of the time, picking a different place each night. I was hiking around Mount Miguel, so that was the general area if you want to check it out on a map. My friend Eric drove me there and then picked me up, and basically I just walked around during the whole two weeks.

Big Sur is beautiful. They say it’s where the land and sea crash together and I couldn’t agree more. It’s so rugged and wild that you can just forget all about cities and towns and the problems of home. I was surrounded by wildlife all the time, including a few bears and a mountain lion.

If you want to go check it out soon then I’ll send you my maps and give you more specific advice, but if you want to wait until spring then I’ll happily take you there myself. I’m going to buy a van and drive back in March, and it’d be great if you came along.




You can see that I have used many contractions here: I’d, it’s, I’m, I’ll, etc. There are also many personal pronouns: I, you, my, they. There are some casual phrases like “check it out” and also some words like “basically” and “all the time” that are possible to use in formal work, but tend to be more suited to informal styles. Also note the features of this letter: I have used my first name and the recipient’s first name, and I have said “Hello” instead of “Dear” and “Best” instead of “Yours sincerely.” These are all really important for setting the tone.

Informal Vocabulary and IELTS Speaking

Of course, all of the above applies to formal writing, but what about IELTS speaking?

The good news is that you don’t have to worry so much about IELTS speaking! It is much more casual. You can use informal language for this section but it doesn’t matter if you also slip in some formal words. For example, in writing we should use transition words (or cohesive devices) such as “however” and “therefore.” In speaking, we more commonly rely on “but” and “and.” We also tend to use words like “so…” to start sentences, even when it is not grammatically correct.

Whilst you are free to use casual language for this part of the exam, I would still remind you not to overdo it. Slang and idioms are fine, but they can be easily misused by learners. Their uses tend to be quite specific and misusing them can result in confusion or even offense.

One other thing is to avoid anything you think could be considered offensive. English changes often these days and some words might have meanings that are offensive. You do not want to say these things to your tutor.

Semi-Formal Writing

Finally, I should mention that “formal” and “informal” are not the only categories. There is also semi-formal writing, which falls somewhere in between the two main categories.

As the name suggests, semi-formal writing may include features of both formal and informal and is used where neither of the previous styles are appropriate. For example, you might need to write a reply to an advertisement in a newspaper. It would be fine to use formal writing but some people might find that a little too much. Instead, they might use mostly formal writing but add some features of informal, such as contractions, idioms, or phrasal verbs:

  • I’m writing to inquire about the table that you are selling.
  • I was over the moon when I received your letter.


Test your knowledge with this formal vs informal language quiz:

formal and informal language quiz


When it comes to IELTS, you should be somewhat familiar with the differences between formal and informal language. The general rule is: Use informal language for speaking and formal language for writing. However, as we have seen, there are a few exceptions to this.

Above all else, make sure that you fully understand any words or phrases before you attempt to use them in IELTS. Making a small mistake is fine, but you do not want to make a big one or else it could lead to real problems.