Unformal or Informal: Which Word Is Correct?

If you are wondering whether “unformal” or “informal” is the correct word, the answer is informal. In standard English, informal is the established adjective used to describe something relaxed, unofficial, casual, or not formal. Oxford and Cambridge both recognize informal with meanings related to relaxed situations and everyday language.

Unformal may appear occasionally in online writing, but it is not the standard choice for normal English. This distinction matters because adding un- to a word does not always create a valid English opposite. If you are writing an email, essay, report, application, or professional message, choose informal.

Quick Answer: Unformal or Informal?

Informal is the correct and standard word in modern English. Unformal is generally considered nonstandard and should be avoided in edited or professional writing.

Examples

• Correct: We had an informal conversation after class.
• Correct: The dress code for the event is informal.
• Correct: She sent me an informal email.

Memory tip: Think formal → informal, not formal → unformal.

What Does Informal Mean?

Informal is an adjective meaning relaxed, casual, unofficial, or not following the rules associated with a formal situation. When talking about language, it can describe words and expressions that are natural in ordinary conversation or communication with friends rather than in highly formal writing. Oxford gives these meanings for both situations and language.

For example, an informal meeting may be relaxed and conversational, while an informal email may use a friendly tone rather than the structure expected in an official letter.

Informal in Everyday English

Informal does not automatically mean incorrect. This is an important distinction.

Consider these examples:

• “Hi, John! How are you?”
• “Thanks for getting back to me.”
• “Can you send me the file?”
• “Let’s talk about it tomorrow.”

These can be perfectly natural English in the right context. They are simply less formal than alternatives such as:

• “Dear Mr. Smith,”
• “Thank you for your response.”
• “Could you please send me the document?”
• “I would like to discuss this matter tomorrow.”

Key takeaway: Informal means less formal or more relaxed; it does not necessarily mean bad, careless, or grammatically incorrect.

Why Is “Unformal” Incorrect?

The confusion comes from the fact that English uses both un- and in- as negative prefixes.

For example:

• happy → unhappy
• fair → unfair
• certain → uncertain
• formal → informal
• complete → incomplete
• responsible → irresponsible

It is tempting to assume that formal → unformal should work because un- often creates an opposite. But English word formation is not completely predictable.

The established opposite of formal is informal, not unformal.

The Prefix Does Not Always Work Logically

English has developed through several languages and historical influences. As a result, you cannot always create a new word simply by attaching a negative prefix.

For example:

• formal → informal
• legal → illegal
• possible → impossible
• regular → irregular
• honest → dishonest
• happy → unhappy

A learner may understand what unformal is supposed to mean, but that does not make it the standard English word.

Key takeaway: Do not choose a negative prefix by logic alone. Learn the established word used by standard English.

Informal vs. Unformal: The Main Difference

The easiest way to understand the difference is to recognize that these two forms do not have equal status in standard English.

Oxford defines informal as something relaxed and friendly and also uses it for language suitable for normal conversation rather than serious or formal writing.

The Simple Rule

When you mean “not formal,” use “informal.”

formal → informal

Do not create:

formal → unformal

When Should You Use Informal?

The word informal is useful in many different situations. Choosing it correctly depends on what you are describing.

Informal Conversation

Use informal for relaxed communication between people who know each other or are speaking in an ordinary conversational setting.

Example:

We had an informal conversation about the project.

This suggests that the conversation was relaxed rather than a formal interview or official meeting.

Informal Emails

An informal email can use a friendly opening, contractions, and conversational wording when the relationship and purpose allow it.

Example:

Hi Sarah,
Thanks for your help. Can we talk about the project tomorrow?

That style may be appropriate when writing to a colleague you know well.

Informal Meetings

An informal meeting may not follow the structure or ceremony of a formal business meeting.

Example:

Let’s have an informal meeting to discuss the new ideas.

The purpose may still be serious. Informal describes the style or setting, not necessarily the importance of the subject.

Informal Clothing

Informal can also describe clothes that are suitable for relaxed or everyday situations. Oxford lists this as another established meaning of the word.

Example:

The invitation says that informal clothing is acceptable.

In this context, informal is close to casual.

Informal Does Not Mean Slang

One common misconception is that all informal English is slang. That is not true.

Informal language is a broad category. Slang is more specific and is often associated with particular groups, situations, or social contexts.

For example:

Oxford specifically distinguishes informal expressions from slang in its usage guidance.

Practical tip: Something can be informal without being slang. Therefore, do not treat the two terms as exact synonyms.

Formal vs. Informal: When Should You Use Each?

The right choice depends on your audience, purpose, and setting.

The important point is that informal does not mean unprofessional in every situation. A workplace chat between colleagues may appropriately use an informal tone, while a contract should not.

A Useful Decision Framework

Before choosing your language style, ask:

Who am I writing to?
→ A friend or close colleague? Informal may be suitable.
→ A client, official, professor, or unfamiliar reader? Use a more formal style.

Why am I writing?
→ Casual conversation? Informal.
→ Official request or academic argument? Formal.

What happens if the tone is too casual?
→ If it could sound disrespectful or careless, make it more formal.

This approach is more useful than trying to memorize a rigid list of “formal words” and “informal words.”

Unformal or Informal: Which Is Correct?

Informal is the correct and standard word in English. It describes something casual, relaxed, or not following formal rules. Unformal is uncommon and generally considered nonstandard, so you should use informal in everyday writing, professional communication, and academic work.

Unformal or Informal Synonyms

Synonyms for informal depend on the context in which you use the word. Common alternatives include:

• Casual: relaxed and not formal.
• Unofficial: not formally authorized or approved.
• Relaxed: free from strict rules or expectations.
• Unconventional: different from traditional practices.
• Colloquial: using everyday, conversational language.
• Conversational: similar to ordinary spoken language.
• Easygoing: relaxed and friendly in manner.

For example, you can describe a meeting as casual, a conversation as informal, or everyday expressions as colloquial. However, these synonyms are not interchangeable in every situation.

Unformal or Informal in English: Meaning and Usage

In English, informal is the standard adjective for describing communication, behavior, clothing, meetings, or events that are not formal.

Here are some common examples:

• Informal conversation: a relaxed conversation between friends.
• Informal meeting: a meeting without a strict structure.
• Informal language: everyday words and expressions.
• Informal dress: clothing suitable for a casual setting.
• Informal invitation: a friendly invitation that does not follow a formal format.

Although unformal may occasionally appear in writing, it is not the usual choice in modern English. In most cases, informal is the natural and correct word.

Unformal or Informal Grammar: What Is the Difference?

From a grammar perspective, informal is the established adjective. It is formed by adding the prefix in- to formal, giving it the opposite meaning.

Examples:

• Formal: Please accept my sincere apologies.
• Informal: Sorry about that!
• Formal: I would appreciate your assistance.
• Informal: Can you give me a hand?

Both formal and informal English follow grammatical rules. However, informal English often uses contractions, everyday expressions, and simpler sentence structures.

For example, I’m gonna call you is common in casual speech, while I’m going to call you is more appropriate in standard writing. The best choice depends on your audience and purpose.

Unformal or Informal Examples in Sentences

These sentences show how to use informal correctly in different contexts.

1. We had an informal meeting to discuss the new project.
2. Her writing style is informal, friendly, and easy to understand.
3. You can wear informal clothes to the family gathering.
4. The teacher encouraged informal discussion among the students.
5. He sent me an informal invitation to his birthday party.
6. Informal language is common when people talk to their friends.
7. The company arranged an informal lunch for its employees.
8. We had an informal conversation about our future plans.

Notice that informal describes a noun in each sentence, such as meeting, style, clothes, or conversation.

Is It Unformal or Informal?

Informal is correct in standard English. Use it when you mean casual, relaxed, or not formal. Avoid unformal in most situations because it is uncommon and generally regarded as nonstandard.

Quick tip: If you are unsure which word to choose, remember that the opposite of formal is usually informal, not unformal.

Common Mistakes With “Unformal”

Mistake 1: Using Unformal as the Opposite of Formal

Wrong:

The meeting was very unformal.

Correct:

The meeting was very informal.

Why it happens: English learners often know that un- can mean “not,” so unformal seems logical.

How to avoid it: Memorize the pair:

formal ↔ informal

Mistake 2: Writing “Unformal Email”

Wrong:

I wrote an unformal email to my manager.

Correct:

I wrote an informal email to my manager.

However, remember that whether an email should be informal depends on your relationship with the recipient and the purpose of the message.

Mistake 3: Assuming Informal Means Incorrect

Incorrect assumption:

Informal English is bad English.

Better understanding:

Informal English is appropriate English for certain situations.

Oxford describes informal language as language suitable for normal conversation and communication with friends, rather than serious speech and letters.

The issue is not whether informal language is “good” or “bad.” The issue is whether it fits the context.

Mistake 4: Using Informal Language in Every Situation

For example:

Hey, what’s up? I need that document ASAP.

This may be perfectly fine in a casual team chat. It may be inappropriate in a formal letter to a university, government office, or new client.

Expert tip: Good writing is not always more formal. Good writing is appropriate for its audience and purpose.

Informal Synonyms and Related Words

Depending on the context, several words can overlap with informal, but they are not always interchangeable.

Casual

Usually describes a relaxed style, appearance, or situation.

We had a casual conversation.

Relaxed

Focuses on an easy, comfortable atmosphere or manner.

The interview was surprisingly relaxed.

Conversational

Often describes language that sounds like natural speech.

The article uses a conversational writing style.

Colloquial

Usually refers to words or expressions commonly used in ordinary speech rather than formal writing.

“Kids” is more colloquial than “children” in many contexts.

Unofficial

Means not official or formally authorized. This is related to informal, but it is not always a direct synonym.

They received unofficial information about the decision.

Key takeaway: Choose the synonym based on the exact meaning you want. “Informal,” “casual,” “conversational,” “colloquial,” and “unofficial” overlap, but they describe different aspects of communication.

Is Informal Appropriate in Academic Writing?

Usually, academic writing favors a formal, precise style. Oxford notes that informal expressions are generally not appropriate for academic writing, although some informal expressions can occur in less formal academic contexts.

Compare:

More formal:

The results indicate that further investigation is necessary.

More conversational:

The results show that we need to look into this more.

The second sentence is understandable, but the first is generally more suitable for a research paper.

This does not mean academic writing should sound complicated. Clear, direct language is usually better than unnecessarily elaborate vocabulary.

Is “Unformal” Ever Acceptable?

For standard modern English, no—there is normally no reason to choose “unformal” when you mean “not formal.”

You may encounter the word in user-generated content, informal online writing, learner writing, or text produced by someone who has formed it by analogy with words such as unfair and unofficial. Seeing a word online does not automatically make it standard English.

If you are writing something that needs to be clear and correct—such as an essay, business email, website article, application, report, or professional document—use informal.

Better:

The event has an informal atmosphere.

Avoid:

The event has an unformal atmosphere.

Expert Tips for Choosing the Right Word

1. Learn word pairs, not isolated words

Instead of remembering only informal, memorize:

formal ↔ informal

This makes the correct choice easier when you write.

2. Check the dictionary label, not just the spelling

A dictionary can tell you whether a word is established and how it is actually used. Oxford and Cambridge both provide entries for informal, confirming its standard meanings.

3. Separate tone from correctness

An informal sentence can be grammatically correct. The question is whether its tone suits the situation.

4. Do not invent opposites

English has many irregular patterns. The fact that un- works in unhappy does not mean it will work with every adjective.

5. Read the whole sentence

Sometimes informal is not even the best replacement for what you mean.

For example:

The announcement was informal.

Could mean the announcement was relaxed or not official.

But if you mean it was not authorized, unofficial may be more accurate.

That small distinction can make professional writing much clearer.

Mini Quiz: Informal or Unformal?

Choose the correct word.

1. We had an ______ discussion after class.
2. The dress code is ______.
3. She sent an ______ message to her friend.
4. The company organized an ______ meeting with the employees.
5. Is “unformal” the standard opposite of “formal”?

Answers

1. informal
2. informal
3. informal
4. informal
5. No. The standard word is informal.

If you remember only one rule from this article, remember:

Formal → Informal

Frequently Asked Questions

Is “unformal” a real English word?

You may occasionally encounter unformal, but it is not the standard word used in modern English when you mean “not formal.” Informal is the established choice.

Is informal the opposite of formal?

Yes. Formal and informal are the standard contrasting terms when describing levels or styles of formality.

Can I use informal in a professional email?

Yes, if the relationship and situation allow it. Communication between familiar colleagues may be informal, while communication with a new client, senior official, or unfamiliar recipient may require a more formal tone.

Does informal mean unprofessional?

No. Informal and unprofessional are different concepts. Informal language can be completely professional when it fits the audience, workplace culture, and purpose.

What is the noun form of informal?

The noun is informality, meaning the quality or condition of being informal. Oxford lists informality alongside informal and informally.

What is the adverb form of informal?

The adverb is informally.

For example:

They discussed the issue informally before the official meeting.

Oxford defines informally as doing something in a relaxed or unofficial way.

Is “unformal” the same as “unofficial”?

No. Informal can mean relaxed or not formal, while unofficial usually means not officially authorized, approved, or confirmed.

Is informal the same as casual?

They often overlap, especially when describing clothing, conversation, or social situations. However, casual can emphasize relaxed style, while informal more directly contrasts with formal.

Is informal English grammatically correct?

It can be. Informal English is a legitimate style of communication. Some informal expressions, however, may be inappropriate in academic or highly formal writing.

Should I use “informal” in an academic essay?

Use it when the meaning requires it, but avoid unnecessarily informal wording. Academic writing generally favors a precise, formal style.

Key Takeaways

• Informal is the correct standard word.
• Unformal should generally be avoided.
• The standard opposite pair is formal ↔ informal.
• Informal does not automatically mean incorrect or unprofessional.
• Informal language is common in conversations, friendly messages, casual meetings, and other relaxed contexts.
• Informal, casual, colloquial, conversational, and unofficial have related but different meanings.
• Choose your tone according to your audience, purpose, and situation.
• Do not assume that the prefix un- can be added to any adjective to create its opposite.

Editorial Note

The key distinction in unformal or informal is not simply spelling. It is a useful lesson in how English word formation works: a word that seems logically possible is not necessarily an established standard word. For reliable writing, follow established dictionary usage rather than constructing an opposite by analogy.

References

• Oxford Learner’s Dictionaries — “informal”: defines informal in relation to relaxed situations, everyday language, clothing, and other contexts.
• Oxford Advanced American Dictionary — “informal”: provides American English definitions and usage information.
• Oxford Learner’s Dictionaries — “informally”: explains the adverbial form and its usage.
• Oxford Learner’s Dictionaries — Language Labels: explains how Oxford distinguishes informal expressions from slang and discusses appropriate contexts.
• Cambridge Learner’s Dictionary — “informal”: defines informal as relaxed, friendly, and suitable for ordinary situations.

Conclusion

When deciding between unformal or informal, choose informal. It is the standard English adjective for something relaxed, casual, or not formal. Although unformal may look logical because English uses un- in many words, it is not the normal standard form.

The easiest way to remember the answer is simple: formal → informal. Before you send an email, submit an essay, or publish an article, use informal when that is the meaning you need.

David James

David James is an English language enthusiast, writer, and author at StudyNixx, a website dedicated to helping readers understand confusing English words, spelling differences, and commonly mistaken word forms. He focuses on making English language learning simple, practical, and easy to understand.

David is also the author of two books on English language and word usage, where he explores common spelling mistakes, confusing words, and practical ways to improve written English. Through his writing and educational content, he helps students, writers, and everyday English learners choose the right words with confidence.

At StudyNixx, David covers common word comparisons such as summary vs. summery, shiny vs. shiney, spicy vs. spicey, and breached vs. breeched. His goal is to provide clear, useful, and reliable explanations that make English spelling and word usage easier for everyone.