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B1 – C1

Formal vs Informal English: The Complete Guide

Everything you need to adjust your English register correctly for any situation, contractions, phrasal verbs, vocabulary and passive voice, with exam practice.

📖 Reading time: ~13 minutes ✅ Reviewed by a CELTA-qualified teacher 🎯 Covers A1 to B2

📋 What's in This Guide

  1. 1. Introduction — Register in English
  2. 2. Quick Summary
  3. 3. Contractions
  4. 4. Phrasal Verbs vs Formal Single-Word Alternatives
  5. 5. Formal vs Informal Vocabulary
  6. 6. Passive Voice in Formal English
  7. 7. Other Formal Features
  8. 8. Common Mistakes
  9. 9. Exercises
  10. 10. Mini Quiz
  11. 11. Exam Focus — Cambridge, IELTS, SELT
  12. 12. Frequently Asked Questions
  13. 13. Related Grammar Guides
  14. 14. Book a Free Level Test

1. Introduction — Register in English

Register means adjusting your language to suit the situation, the same idea can be expressed very differently depending on whether you're texting a friend or writing a formal report. Choosing the wrong register, using slang in a job application, or being overly formal in a casual chat, is a genuine communication error, even when the grammar itself is technically correct.

This guide brings together the specific features that separate formal and informal English, many of which connect directly to other grammar points covered elsewhere on this site.

2. Quick Summary

⚡ Formal vs Informal at a Glance

InformalContractions, phrasal verbs, simple vocabulary, active voice
FormalFull forms, single-word verbs, precise vocabulary, passive voice
Example"I can't make it" (informal) vs "I am unable to attend" (formal)
Common MistakeUsing contractions and phrasal verbs in a formal cover letter or academic essay

3. Contractions

Contractions (can't, don't, I'm, it's) are standard in informal and neutral English, but generally avoided in formal writing, academic essays, and official documents.

InformalFormal
I can't attend the meeting.I am unable to attend the meeting.
We don't have enough data.We do not have sufficient data.
It's important to note...It is important to note...

4. Phrasal Verbs vs Formal Single-Word Alternatives

As covered in our full guide to phrasal verbs, informal English relies heavily on them, while formal writing generally prefers a single-word Latinate alternative.

Informal (phrasal verb)Formal (single word)
find outdiscover
put offpostpone
set upestablish
look intoinvestigate
give upabandon

5. Formal vs Informal Vocabulary

InformalFormal
kidschildren
a lot of / lots ofa significant number of / considerable
getreceive / obtain
guy / blokeman / gentleman
okay / finesatisfactory / acceptable

6. Passive Voice in Formal English

As covered in our full guide to the passive voice, formal and academic writing uses the passive far more often than everyday speech, since it sounds more objective and removes personal focus.

Informal (active)Formal (passive)
We conducted the survey in March.The survey was conducted in March.
Someone made a mistake in the report.A mistake was made in the report.

7. Other Formal Features

FeatureInformalFormal
Question tagsYou're coming, right?Will you be attending?
Starting with "and/but"And that's why we left.Consequently, we left.
Direct addressHey, thanks for this!Thank you for your assistance.

8. Common Mistakes

❌ Too Informal (in a formal context)✅ Correct Formal RegisterWhy
I can't make the meeting, sorry!I regret that I am unable to attend the meeting.Contractions and casual phrasing don't fit a formal email or letter.
We need to look into this problem.We need to investigate this issue. (in an academic report)A phrasal verb reads as too casual for formal or academic writing.
Lots of people think this is wrong.A significant number of people consider this incorrect."Lots of" and "think" are too informal for academic register.

9. Exercises

A. Gap Fill — Rewrite in the correct register (7 questions)

1. Make formal: "I can't come to the party." → I ___ unable to attend.
2. Make formal: "We need to look into this." → We need to ___ this. (investigate)
3. Make formal: "Lots of people agree." → A ___ number of people agree.
4. Make formal: "It's a good idea." → It ___ a good idea.
5. Make formal: "We found out the truth." → We ___ the truth. (discovered)
6. Make informal: "I am unable to attend." → I ___ come.
7. Make formal: "The kids were playing outside." → The ___ were playing outside.
Show Answers (A)
1. am   2. investigate   3. significant   4. is   5. discovered   6. can't   7. children

B. Multiple Choice (4 questions)

1. Which is more formal? (a) I can't make it. (b) I am unable to attend.
2. Which is more formal? (a) We looked into it. (b) We investigated it.
3. Which is more formal? (a) Lots of people. (b) A significant number of people.
4. Which is more formal? (a) The survey was conducted in March. (b) We did the survey in March.
Show Answers (B)
1.b 2.b 3.b 4.a

C. Error Correction — Fix the Register (3 questions)

1. Formal email: "I can't make the meeting, sorry!"
2. Academic essay: "We need to look into this problem."
3. Formal report: "Lots of people think this is wrong."
Show Answers (C)
1. I regret that I am unable to attend the meeting.
2. We need to investigate this issue.
3. A significant number of people consider this incorrect.

D. Freer Practice — Rewrite in the Opposite Register (2 tasks)

1. Rewrite this informal sentence formally: 'I can't come, sorry, something came up.'
2. Rewrite this formal sentence informally: 'I regret that I am unable to attend due to a prior commitment.'
Show Answers (D)
Model answers will vary. Examples:
1. "I regret that I am unable to attend due to a prior commitment."
2. "Sorry, can't make it, something's come up."

10. Mini Quiz

1. Which is more formal?

2. Which is more formal?

3. Which is more informal?

4. Which fits an academic essay better?

11. Exam Focus — Cambridge, IELTS, SELT

ExamHow Register Is TestedSample Question
Cambridge B2 First / C1 AdvancedThe Writing paper includes both formal (report, essay) and informal (email, review) task types, testing appropriate register control.Writing a formal report to a manager vs an informal email to a friend on the same topic.
IELTS Writing Task 1 (General Training)Candidates must adjust register precisely depending on whether the letter is formal, semi-formal or informal.Writing a formal complaint letter vs an informal letter to a friend.
IELTS Writing Task 2The academic essay expects consistently formal register throughout, no contractions, no phrasal verbs.Avoiding contractions and casual vocabulary in an argumentative essay.
Trinity GESE/ISE (SELT)Higher levels assess the ability to shift register appropriately depending on the conversational context.Speaking more formally in a simulated professional scenario.

12. Frequently Asked Questions

The level of formality in language, adjusted to suit the situation, audience and purpose, from casual texting to formal academic writing.
Generally no — formal writing, academic essays and official documents typically avoid contractions like can't, don't and it's, using the full forms instead.
Generally avoid them where a single-word alternative exists, use 'investigate' instead of 'look into,' or 'postpone' instead of 'put off,' in formal contexts.
Because it sounds more objective and impersonal, which suits academic and official writing, where the focus is on the action or result, not who did it.
Generally yes, in traditional formal writing, though this rule is relaxing somewhat even in modern formal contexts.
At higher levels, yes, the ability to shift between casual and more formal register appropriately is assessed in some speaking scenarios.

📅 Ready to Master Formal and Informal English — for Any Situation?

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