Unformal or Informal: Correct Word Choice and Usage

Unformal or informal? In standard modern American English, informal is the word you should normally use when you mean “not formal,” “casual,” “relaxed,” or “unofficial.” Unformal may be understandable, and rare or historical evidence exists, but it is not the normal modern choice.

This confusion is easy to understand. English often uses un- to create opposites, as in unhappy and unclear. However, English does not build every opposite with the same prefix. The established adjective is informal, formed with in-.

The key is therefore simple: if you want the standard adjective meaning “not formal,” choose informal.

Quick Answer

For unformal or informal, choose informal in standard modern English. It describes something that is not formal, official, ceremonial, or highly structured. Use it for phrases such as informal meeting, informal language, and informal clothing. Although unformal may appear in rare or historical contexts, it is not the normal word for modern U.S. writing.

TL;DR

• Informal is the standard modern word.
• Unformal is unusual and normally best avoided.
• Informal can mean casual, relaxed, unofficial, or conversational.
• Informal does not automatically mean rude or unprofessional.
• Casual and relaxed overlap with informal, but they are not perfect substitutes.
• The opposite of informal is usually formal.

Unformal or Informal at a Glance

Feature	Informal	Unformal
Standard modern U.S. choice	Yes	No
Basic meaning	Not formal; casual or unofficial	Intended to mean “not formal”
Common in edited writing	Yes	No
Natural phrases	informal meeting, informal tone	No common standard patterns
Can describe language?	Yes	Not normally
Can describe clothing?	Yes	Not normally
Best advice	Use it	Avoid it in normal writing

Merriam-Webster lists informal as an adjective meaning marked by an absence of formality or ceremony and also as suitable for ordinary, casual, or familiar use. Cambridge likewise uses the word for things that are not formal or official and for speech, behavior, and clothing suited to less formal situations.

Why Informal Is the Standard Choice

The correct modern choice is informal.

English does not always form negative adjectives by simply adding un-. Compare these established forms:

• happy → unhappy
• clear → unclear
• fair → unfair
• formal → informal
• accurate → inaccurate
• legal → illegal
• regular → irregular

The pattern depends partly on the history and structure of each word. That means you cannot reliably create a new opposite by attaching un- whenever the meaning seems logical.

The safest approach is to learn the established form rather than assume the prefix.

For example:

• Correct: The meeting was informal.
• Incorrect in standard modern usage: The meeting was unformal.

The same rule applies in professional and academic writing. If you mean that something is relaxed or not official, informal is the established choice. Merriam-Webster, Cambridge, and Oxford all document informal as a standard adjective.

For a direct dictionary reference, see the

Merriam-Webster definition of informal.

What Does Informal Mean?

Informal has several closely related meanings. The exact sense depends on what it describes.

Oxford defines it in contexts involving relaxed or friendly behavior, language suitable for ordinary conversation, informal clothing, and certain unofficial forms of work or business.

1. Not formal or ceremonial

An informal event is relaxed rather than highly structured or ceremonial.

We had an informal dinner after the conference.

2. Casual or relaxed

An informal atmosphere feels comfortable rather than stiff or highly official.

The restaurant has an informal atmosphere.

3. Conversational language

Informal language is appropriate for ordinary conversation and familiar communication.

“Thanks for your help” sounds natural in many informal messages.

4. Unofficial or less structured

An informal arrangement may exist without a formal process or official structure.

The two departments reached an informal agreement.

5. Suitable for everyday use

Informal clothing, for example, is suitable for relaxed situations rather than special or formal occasions.

The invitation says that the dress code is informal.

These meanings overlap, but they are not identical. Context tells you which part of the meaning is most important.

Why “Unformal” Causes Confusion

The form unformal looks reasonable because un- often means “not.”

That creates a tempting pattern:

formal → unformal

But standard English does not use that form as the ordinary modern opposite of formal.

This is similar to other words where the apparently logical negative form is not the established word. English learners cannot always predict which negative prefix a word takes.

Another reason for the confusion is that unformal is easy to understand. A reader can usually guess what the writer means. However, being understandable does not make a form the best standard choice.

Compare:

The teacher used an informal teaching style.

with:

The teacher used an unformal teaching style.

The first sounds natural. The second may make readers stop and wonder whether it is a mistake.

That is why the practical rule is more useful than trying to invent a prefix rule:

When you mean “not formal,” use informal.

Some sources discuss rare or historical evidence for unformal, so it is better to describe the word as unusual or nonstandard in ordinary modern usage rather than claim that the sequence of letters can never appear in English.

Formal vs Informal: Tone and Register

Informal does not mean bad, careless, or rude.

It describes a level or style of formality. A message can be informal and still be polite, thoughtful, and professional.

For example:

Formal:

Dear Ms. Carter, I am writing to confirm our appointment.

Informal but polite:

Hi Maya, just checking that we’re still meeting tomorrow.

Both can be appropriate. The best choice depends on the audience, relationship, purpose, and setting.

Cambridge describes informal as appropriate for situations with friends and family rather than official occasions, while Oxford applies the word to relaxed language, meetings, clothing, and arrangements.

A useful scale is:

formal → neutral → informal → very casual

For example:

• Formal: “I would appreciate your response.”
• Neutral: “Please let me know what you think.”
• Informal: “Let me know what you think.”
• Very casual: “Tell me what you think!”

Not every situation fits neatly into this scale, but it helps explain why informal is a register label rather than an insult.

Informal vs Casual, Relaxed, and Unofficial

Several words are close to informal, but they are not perfect synonyms.

Word	Core idea	Example
informal	Not formal or official	an informal meeting
casual	Relaxed or unconcerned	casual clothes
relaxed	Calm and free from tension	a relaxed atmosphere
unofficial	Not formally authorized	an unofficial announcement
colloquial	Characteristic of everyday speech	a colloquial expression

These words can overlap.

For example:

We had an informal meeting.

You could sometimes say:

We had a casual meeting.

But the two sentences are not always identical. Informal focuses on the level of formality. Casual can emphasize a relaxed or unplanned character.

Likewise:

The announcement was unofficial.

does not necessarily mean:

The announcement was informal.

An unofficial announcement may still use very formal language.

Similarly, colloquial is mainly useful when discussing language associated with ordinary conversation. Oxford contrasts informal language with formal language, while Collins also recognizes informal for everyday conversational language.

For more examples of how English word choices can depend on grammatical function, EnglishShub’s guide to

Aide or Aid

provides a useful comparison.

Informal, Informality, and Informally

The word family includes more than the adjective informal.

Informal — adjective

Use informal to describe a person, thing, situation, style, or type of language.

The interview was informal.

She prefers informal clothing.

Informality — noun

Use informality to name the quality or condition of being informal.

The informality of the meeting helped everyone relax.

Informally — adverb

Use informally to describe how something happens.

The two managers spoke informally before the meeting.

Cambridge lists informally as an adverb meaning in a way that is not formal or official, while Merriam-Webster gives informality and informally as related forms of informal.

This gives you a useful word-family pattern:

informal → informality → informally

Do not create unformal simply because the adjective seems as though it should have an un- prefix.

Common Mistakes and Corrections

Mistake 1: Using unformal

Incorrect:

We had an unformal meeting.

Correct:

We had an informal meeting.

Mistake 2: Writing “in formal” when you mean informal

Incorrect:

Her writing style is in formal.

Correct:

Her writing style is informal.

However, in formal can be correct when in is a separate preposition and formal is an adjective:

She spoke in formal English.

Here, in belongs to the prepositional phrase, so it should remain separate.

Mistake 3: Assuming informal means unprofessional

Incorrect idea: Informal writing is always careless.

Better understanding: Informal writing can be clear, polite, and appropriate when the audience and situation allow it.

Mistake 4: Treating informal and casual as identical

Incorrect assumption: Every use of informal can be replaced with casual.

Better: Check the intended meaning first.

The discussion was informal.

This may mean that it was unofficial or less structured. Casual could suggest something more relaxed, but it does not always preserve the same emphasis.

Mistake 5: Using informal when you mean illegal

An informal arrangement is not automatically illegal.

They reached an informal agreement.

This means the agreement was not formalized in the usual way. It does not, by itself, tell you whether the arrangement was lawful.

When “Unformal” May Appear

For ordinary modern American English, informal is the safe choice.

Still, language sources can contain rare, historical, specialized, or quoted forms. Wiktionary, for example, records unformal as an adjective meaning “not formal.”

That does not mean you should routinely replace informal with unformal. The important distinction is between existence in some evidence and standard modern usage.

If you encounter unformal in an old text, a quotation, a historical source, or a specialized context, preserve the original wording when you are reporting or quoting that source.

For normal writing today, however:

Use informal.

This distinction matters because dictionaries can record words that are rare, dated, regional, historical, or otherwise marked. A word’s appearance in a source does not automatically make it the preferred choice for contemporary U.S. prose.

Examples of Informal in Everyday English

Here are natural examples across different contexts:

1. The company held an informal meeting after lunch.
2. Her email sounded friendly and informal.
3. The invitation called for informal dress.
4. We had an informal conversation before the interview.
5. The teacher encouraged an informal discussion.
6. The two teams reached an informal agreement.
7. His writing style is clear but informal.
8. The event had an informal atmosphere.
9. The manager asked for some informal feedback.
10. The students spoke informally during the activity.

Now compare them with the nonstandard choice:

• Avoid: an unformal meeting
• Use: an informal meeting
• Avoid: an unformal tone
• Use: an informal tone
• Avoid: unformal language
• Use: informal language
• Avoid: an unformal event
• Use: an informal event

The meaning is usually obvious even with unformal, but standard word choice makes the sentence sound natural and polished.

EnglishShub’s recent guides use the same practical approach for other word-choice problems, such

as Therefor or Therefore and One in the Same or One and the Same.

A Simple Three-Step Test

When you are unsure about unformal or informal, use this test.

Step 1: Ask what you mean

Do you mean:

• not formal?
• casual?
• relaxed?
• conversational?
• unofficial?

If yes, informal is probably the word you need.

Step 2: Put the word into a common phrase

Try:

• informal meeting
• informal language
• informal email
• informal clothing
• informal discussion
• informal agreement
• informal tone

If the phrase sounds natural, informal is the established choice.

Step 3: Check whether you actually mean something more specific

Sometimes informal is too broad.

For example:

The party has a relaxed atmosphere.

may be more precise than:

The party has an informal atmosphere.

Likewise:

The announcement was unofficial.

may be better than:

The announcement was informal.

So the final rule is not simply “always choose informal.” It is:

Choose informal when your intended meaning is “not formal”; choose a more specific word when that better describes the situation.

FAQs

Test Your Understanding

1. Which sentence uses the standard word?

A. We had an unformal meeting.
B. We had an informal meeting.
C. We had an in formal meeting.
D. We had a nonformal meeting in every context.

2. What does “informal” usually mean in “informal conversation”?

A. Illegal conversation
B. Secret conversation
C. Relaxed or conversational communication
D. Incorrect conversation

3. Which sentence uses “in formal” correctly as two separate words?

A. Her style was in formal.
B. The meeting was in formal.
C. She spoke in formal English.
D. He wrote an in formal email.

4. Which word is the best choice if you mean “not officially authorized”?

A. informal
B. casual
C. unofficial
D. relaxed

5. Which sentence uses the noun form correctly?

A. The informality of the gathering made guests comfortable.
B. The informal of the gathering made guests comfortable.
C. The informally of the gathering made guests comfortable.
D. The unformal of the gathering made guests comfortable.

Answer Key

1. B — Informal is the standard modern adjective for something that is not formal.
2. C — Informal conversation means relaxed or everyday conversational communication.
3. C — Here, in is a preposition and formal describes the type of English.
4. C — Unofficial specifically emphasizes a lack of official authorization or status.
5. A — Informality is the noun naming the quality or condition of being informal.

Conclusion

When choosing unformal or informal, use informal when you mean “not formal,” “casual,” “relaxed,” or “unofficial.” It is the established modern adjective in American English and works naturally in phrases such as informal meeting, informal language, and informal tone.

Unformal can appear in rare or historical evidence, but it is not the normal choice for contemporary edited writing. Remember the simplest rule: formal → informal, not unformal.

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One in the Same or One and the Same: Meaning and Correct Use