Cannot vs Can Not: Which Is Correct?

The question of whether to write "cannot" or "can not" confuses many English writers. While both forms exist, one is the standard choice in nearly all situations. This guide will help you understand the difference and use the correct form.

Quick Answer

• Cannot = the standard, correct form (one word) - use this 99% of the time
• Can not = two words, used only for special emphasis (very rare)

Cannot: The Standard Form

Cannot is written as one word and is the standard negative form of "can." This is the form you should use in almost all writing.

Definition:

Cannot means "to be unable to" or "to not be permitted to."

Examples of "Cannot":

• I cannot swim.
• She cannot attend the meeting.
• We cannot solve this problem alone.
• You cannot park here.
• They cannot arrive before noon.
• Students cannot use phones in class.

Different Forms:

• Cannot (formal writing)
• Can't (informal, spoken, contractions allowed)

Both mean the same thing; can't is just the contracted form.

Can Not: The Rare Two-Word Form

Can not (two words) is technically correct but should only be used in very specific situations where you want to emphasize the word "not."

When to Use "Can Not" (Two Words):

The two-word form is used only when you want to place special emphasis on the word "not," usually contrasting it with something else.

Rare Examples Where Two Words Work:

1. Contrasting "can" and "cannot":

   • You can not go, or you can stay—it's your choice.
   • (Meaning: it's possible for you NOT to go)

2. Emphasizing the negative:

   • I can not only dance, but also sing.
   • (Here "not only" is a phrase)

3. Special emphasis in formal speech:

   • We can not, and we will not, tolerate this behavior.
   • (Very emphatic, formal speech)

Important Note:

Even in these cases, many style guides and grammarians recommend using "cannot" or rephrasing the sentence. The two-word form is extremely rare in modern English.

Why "Cannot" Is Almost Always Correct

Historical Development:

Originally, "can not" was two words, but over time, they merged into one word: "cannot." This is now the universally accepted standard form.

Modern Usage:

• Cannot is used 99%+ of the time
• Can not is considered unusual or archaic
• Most style guides recommend always using cannot

Grammar Rules:

Unlike some other negative constructions that stay as two words (like "may not" or "might not"), "can" combines with "not" to form a single word.

Comparison with Other Negative Forms

One Word (Like Cannot):

• Cannot - ✓ (one word)

Two Words (Unlike Cannot):

• May not - ✓ (two words)
• Might not - ✓ (two words)
• Should not - ✓ (two words)
• Will not - ✓ (but contracts to won't)
• Must not - ✓ (two words)
• Could not - ✓ (two words, but could also be couldn't)

Cannot is unique as a modal verb negative that's written as one word.

Common Mistakes and Corrections

✗ Incorrect Usage:

1. I can not swim. (Wrong - use "cannot")
2. She can not come to the party. (Wrong - use "cannot")
3. We can not afford this. (Wrong - use "cannot")
4. You can not enter without a ticket. (Wrong - use "cannot")

✓ Correct Usage:

1. I cannot swim.
2. She cannot come to the party.
3. We cannot afford this.
4. You cannot enter without a ticket.

The Contracted Form: Can't

In informal writing and speech, "cannot" is often contracted to can't.

When to Use "Can't":

• Informal writing: emails to friends, texts, casual notes
• Spoken English: everyday conversation
• Informal business communication: some workplace emails
• Creative writing: dialogue, informal narratives

When to Use "Cannot":

• Formal writing: academic papers, business reports
• Official documents: contracts, legal writing
• Professional communication: formal letters, proposals
• Published writing: books, articles (unless dialogue)

Examples:

Informal:

• I can't believe it!
• She can't make it tonight.
• We can't wait!

Formal:

• The company cannot accept liability.
• Students cannot submit assignments late.
• This policy cannot be changed.

Special Cases and Exceptions

The Only Time "Can Not" (Two Words) Might Be Used:

1. When "not" is part of another phrase:

• I can not only sing but also dance.
  • (Here, "not only...but also" is a phrase)
  • Better: I can sing and also dance.

2. When emphasizing choice:

• You can not answer if you prefer.
  • (Meaning: you have the option NOT to answer)
  • Better: You can choose not to answer.
  • Or: You don't have to answer.

3. In very formal, emphatic speech:

• We can not and will not surrender!
  • (Very emphatic)
  • Better: We cannot surrender!

Bottom Line: Even in these cases, using "cannot" or rephrasing is almost always better.

Style Guide Recommendations

Major Style Guides Say:

Chicago Manual of Style:

• Use cannot (one word)

AP Stylebook:

• Use cannot (one word)

MLA Style:

• Use cannot (one word)

Oxford Style Guide:

• Use cannot (one word)

Conclusion: All major style guides agree—use cannot as one word.

Memory Tricks

1. Default to One Word:

Cannot is ALWAYS correct. When in doubt, use cannot.

2. Think of It Like "Into" or "Onto":

Just as we write "into" and "onto" as one word, we write cannot as one word.

3. Remember the Rule:

Can + not = Cannot (one word, no exceptions in normal writing)

4. Visual Reminder:

Cannot = CAN + NOT = CANNOT ✓ Can not = CAN NOT = ✗ (wrong 99% of the time)

Practice Examples

Correct Form:

1. I cannot attend the meeting tomorrow.
2. She cannot solve the puzzle alone.
3. We cannot guarantee results.
4. They cannot park in this area.
5. You cannot bring food into the theater.
6. The system cannot process this request.
7. He cannot swim very well.
8. Children cannot purchase tickets.

Informal (Contracted):

1. I can't make it tonight.
2. She can't believe what happened.
3. We can't wait to see you!
4. They can't stop laughing.

Common Expressions

Always Written as One Word:

• Cannot help but (I can't help but agree)
• Cannot afford to
• Cannot stand (I cannot stand the noise)
• Cannot wait
• Cannot believe
• Cannot deny
• Cannot ignore
• Cannot fail
• Cannot be helped

Summary Table

Form	Status	When to Use
Cannot	✓ Correct	Always (formal writing)
Can't	✓ Correct	Informal writing/speech
Can not	⚠️ Rarely	Almost never (special emphasis only)

Quick Decision Guide

Question: Should I write "cannot" or "can not"?

Answer: Write cannot (one word).

Exception: Are you a professional writer crafting a very specific emphatic construction where "not" needs unusual stress?

• Yes → You might (rarely) use "can not"
• No → Use cannot

In 99.9% of cases: Use cannot

Practice Exercises

Correct the sentences if needed:

1. I can not find my keys.
2. She cannot speak Spanish.
3. We can not afford this car.
4. They can not arrive before 6 PM.
5. You can not enter without ID.

Answers:

1. ✗ → I cannot find my keys.
2. ✓ (already correct)
3. ✗ → We cannot afford this car.
4. ✗ → They cannot arrive before 6 PM.
5. ✗ → You cannot enter without ID.

British vs American English

Both British and American English follow the same rule:

• Cannot = standard (one word)
• Can't = contracted form
• Can not = extremely rare

There is no difference between British and American usage on this point.

Conclusion

The answer is simple: always use "cannot" as one word. While "can not" (two words) is technically possible in extremely rare emphatic constructions, it's so uncommon that you should default to "cannot" in all your writing.

Remember:

• ✓ Cannot - use this always
• ✓ Can't - informal/spoken
• ✗ Can not - avoid (unless you're a professional writer with a very specific reason)

When in doubt, stick with cannot—you'll be correct every time!