Formal vs Informal English
Learn how vocabulary, contractions, sentence structure and tone shift between formal and informal English, and how to choose between them.
Two registers, one language
Formal and informal English serve different situations.
Formal English is used in situations that call for distance, precision and a professional tone, such as official letters, academic writing or communication with someone unfamiliar. Informal English is used in relaxed situations, such as conversations with friends or casual messages, and allows for contractions, simpler vocabulary and a more personal tone.
In the sentences Could you send me the report by Friday? and Can you send me the report by Friday?, both are grammatically correct. The choice between them depends on who is being addressed, and how much distance or familiarity the situation calls for.
Neither register is more “correct” than the other. Each is appropriate in its own context, and part of communicating effectively in English is recognising which one a situation calls for.
Before you begin
Formal vs informal English is one topic within Grammar in Context.
This lesson focuses on the difference between formal and informal English specifically. For an overview of the topic as a whole, including links to every related lesson, begin with the Grammar in Context page.
The central idea
Formal English adds distance; informal English adds familiarity.
Compare the same request in each register.
01
Formal
Full words, indirect requests, a measured tone.
Could you send me the report by Friday?
02
Informal
Contractions, direct requests, a relaxed tone.
Can you send me the report by Friday?
Both requests are grammatically correct.
The difference is not accuracy, but register. Choosing between them depends on the relationship between the speakers and the situation they are in.
Contractions
Contractions are common in informal English and avoided in formal English.
Informal, with a contraction
I don’t have time today.
Formal, written in full
I do not have time today.
Formal writing generally spells out contractions such as don’t, can’t and it’s, in full.
Vocabulary choices
Formal English often prefers a single, precise word over a phrasal verb.
Buy, compared with purchase
Informal: We need to buy new equipment.
Formal: We need to purchase new equipment.
Find out, compared with determine
Informal: We need to find out what happened.
Formal: We need to determine what happened.
Phrasal verbs like find out are common in informal English; formal English often replaces them with a single word of similar meaning.
Get in touch, compared with contact
Informal: Get in touch if you have questions.
Formal: Please contact us if you have any questions.
Sentence structure
Formal English favours the passive voice and fuller sentences.
Active voice, informal
We made a mistake in the report.
Passive voice, formal
A mistake was made in the report.
The passive voice shifts focus away from who performed the action, which suits the more impersonal tone of formal writing.
Shortened sentences, informal
Not sure yet. Let you know soon.
Informal English, especially in speech and messaging, often drops the subject or auxiliary verb; formal English keeps sentences grammatically complete.
Requests and questions
Formal requests are often more indirect than informal ones.
A direct informal request
Send me the file.
An indirect formal request
I would be grateful if you could send me the file.
Adding distance to a request, through modal verbs and longer phrasing, is one of the clearest markers of formal English.
A useful decision guide
Ask who the audience is, and how much distance the situation calls for.
01
Is the reader or listener unfamiliar, or in a position of authority?
Formal English generally fits better.
02
Is the setting official, such as a report, application or academic paper?
Formal English is expected, including avoiding contractions.
03
Is the reader or listener a friend, family member or close colleague?
Informal English usually fits the relationship better.
Common mistakes
Do not mix registers within the same piece of writing.
Mixing contractions into formal writing.
Not: We don’t recommend this approach, based on the findings.
Correct: We do not recommend this approach, based on the findings.
Once a formal tone is set, contractions should be avoided consistently, not just some of the time.
Using overly formal language in a casual message.
Not: I would be grateful if you could pass the salt.
Correct: Can you pass the salt?
Excessive formality in a casual setting can sound unnatural or overly distant.
Assuming informal English is grammatically incorrect.
Can you send me the report by Friday?
This sentence is grammatically correct; it is simply less formal than an alternative with “could.”
Informal English follows its own grammatical rules; it is a different register, not an incorrect one.
Check your understanding
Is the register used correctly?
Choose the correct answer for each sentence.
Which sentence is more appropriate for a formal report?
✅ Exactly! The passive voice suits the more impersonal tone of formal writing.
❎ Not quite. Compare which sentence shifts focus away from who made the mistake.
Formal English often favours the passive voice.
Which sentence is more appropriate for formal writing?
✅ Exactly! Formal writing generally spells out contractions in full.
❎ Not quite. Check whether a contraction is used here.
“I would be grateful if you could pass the salt.” Is this appropriate at a casual family dinner?
✅ Exactly! Excessive formality in a casual setting can sound unnatural.
❎ Not quite. Think about how distant this phrasing sounds for a family dinner.
“Can you send me the report by Friday?” Is this sentence grammatically incorrect?
✅ Exactly! Informal English follows its own grammatical rules; it is a different register, not an incorrect one.
❎ Not quite. Consider the difference between register and grammatical accuracy.
Choose the best explanation
Select the sentence that explains the register correctly.
Why is “Could you send me the report by Friday?” often chosen over “Can you send me the report by Friday?” in a formal email?
✅ Exactly! The choice of modal verb shapes how formal a request sounds.
❎ Not quite. Both versions are grammatically correct; think about the tone each one creates.
Why does formal English often replace phrasal verbs like “find out” with single words like “determine”?
✅ Exactly! Vocabulary choice is one of the clearest signals of register.
❎ Not quite. Phrasal verbs are correct English; think about the tone they carry instead.
Why is mixing contractions into an otherwise formal report considered a mistake?
✅ Exactly! Once a formal tone is set, it needs to stay consistent throughout.
❎ Not quite. Think about what happens when formal and informal features appear side by side.
Try it another way
Complete each sentence with the correct word or form.
Type the missing word or words shown in brackets.
✅ Exactly! Formal writing spells out contractions in full.
❎ Not quite. Write “do not” in full, without a contraction.
✅ Exactly! “Purchase” is the more formal equivalent of “buy.”
❎ Not quite. Think of the more formal word for “buy.”
✅ Exactly! The passive voice fits the formal, impersonal tone here.
❎ Not quite. Use the passive form of “make.”
Edit the sentence
Rewrite each sentence in the register requested.
Use the note in brackets to decide what needs to change.
I don’t have time today. (rewrite in formal English)
✅ Exactly! Writing “do not” in full matches a formal register.
❎ Not quite. Expand the contraction “don’t” to “do not.”
I would be grateful if you could send me the file. (rewrite in informal English)
✅ Exactly! A shorter, more direct request suits an informal register.
❎ Not quite. Simplify the request to a shorter, more direct question.
We need to find out what happened. (rewrite in formal English)
✅ Exactly! “Determine” replaces the phrasal verb “find out” in formal English.
❎ Not quite. Replace “find out” with a single, more formal word.
Quick review
Register is a choice about audience, purpose and situation.
Formal English avoids contractions, favours precise vocabulary and the passive voice, and adds distance to requests.
Informal English uses contractions, phrasal verbs and more direct requests, suited to relaxed situations.
Neither register is more grammatically correct than the other; each fits a different context.
Mixing registers within the same piece of writing usually reads as inconsistent.
The right choice depends on the audience, the purpose and how much distance the situation calls for.
Remember
Ask who is reading or listening, and how much distance the situation calls for.
Once that’s clear, the choice of vocabulary, contractions and sentence structure tends to follow naturally, matching the tone the audience and purpose actually call for.