can not (cannot)

The common confusion is simple: write cannot as one word in nearly all negative uses of can. The two-word form can not is rarely correct and only fits when not belongs to a different phrase (for example, not only) or when you're separating not from can for a specific contrast or construction.

Quick answer

Use cannot (one word) as the standard negative of can. Use can not (two words) only when not is part of a different phrase or meaning.

• Standard negative: I cannot finish today. / I can't finish today.
• Different construction: You can choose not to attend. (not attaches to choose, not to can)

Is "can not" ever correct?

Usually no. In edited English, cannot is the expected negative of can. Use can not only when not belongs to another element in the sentence (for example, "not only") or when the sentence structure puts not with a different verb or infinitive.

Examples of the correct exception:

• You can not only save money but also invest it. (not pairs with only)
• You can choose not to go if you prefer. (not modifies choose)

Core explanation

Cannot is the single-word contraction of can + not that marks inability, impossibility, or prohibition. It's the predictable, grammatical negative form.

Can not, as two words, breaks that unit. It's only natural when the writer intends not to attach to can itself but to another element that follows or when contrasting choices.

Why writers split the form

Writers separate can and not for a few predictable reasons:

• They hear the parts in speech and guess at spacing.
• They confuse negation that belongs to a following verb or phrase.
• They edit quickly and overlook the standard written form.

Real usage - natural examples

Seeing the forms in context helps lock the correct choice into place.

• Work: We cannot release the update until QA signs off. / You can not only review the code but also suggest improvements.
• School: I cannot submit the assignment after midnight. / Students can not only read the chapter but also present a summary.
• Casual: I cannot make dinner tonight. / You can choose not to come if you're tired.

Wrong vs right examples you can copy

Six quick pairs you can paste into your drafts and keep as a reference.

• Wrong: The team can not complete the sprint by Friday.
  Right: The team cannot complete the sprint by Friday.
• Wrong: She can not attend the ceremony.
  Right: She cannot attend the ceremony.
• Wrong: We can not accept late refunds.
  Right: We cannot accept late refunds.
• Wrong: You can not only improve speed but also reduce costs.
  Right: You can not only improve speed but also reduce costs. (acceptable because not pairs with only)
• Wrong: Is it true you can not swim?
  Right: Is it true you cannot swim?
• Wrong: Dinner at seven can not work for me.
  Right: Dinner at seven cannot work for me.

How to fix your own sentence

Fixing the mistake usually takes two quick checks: decide what not attaches to, then choose cannot or a rewording.

1. Identify whether not negates can itself.
2. If it does, replace with cannot or can't.
3. If not attaches to another verb or phrase, rephrase so meaning is clear (for example, "choose not to").

• Rewrite:
  Original: This plan can not work if we lose staff.
  Rewrite: This plan cannot work if we lose staff.
• Rewrite:
  Original: The assignment can not be finished tonight.
  Rewrite: The assignment cannot be finished tonight.
• Rewrite:
  Original: Can not this be fixed by Thursday?
  Rewrite: Can this not be fixed by Thursday? (here not follows the auxiliary to emphasize the question)

Hyphenation and spacing notes

There's no hyphen in cannot. Treat it as one closed word. Similar spacing errors occur with words like into/ in to, altogether/ all together, and so on; check common dictionary forms when unsure.

Grammar note

Use cannot for the simple negative. Use can not only when not combines with another word (not only) or when the grammar places not with a different verb. Avoid splitting cannot without a clear structural reason.

A simple memory trick

Picture cannot as a single unit that blocks action: it's one word because it blocks the verb. If you can mentally "zap" the action, write cannot. If not pairs with another word (not only) or you mean "choose not to," treat not separately.

• Think "cannot = cannot do it."
• If you say "not only" or "choose not to," keep not separate.
• Search your draft for "can not" and fix in bulk when you find cases that should be cannot.

Similar mistakes to watch for

These split-or-closed problems appear elsewhere. After fixing cannot, scan for:

• into vs. in to
• altogether vs. all together
• everyday vs. every day
• hyphen usage in compound modifiers

FAQ

Is "can not" ever correct?

Rarely. Use it when not belongs to another element (for example, "not only") or when the structure requires it. Otherwise use cannot.

Should I use can't instead?

Can't is the contracted spoken/written form of cannot and works well in informal writing. Use cannot for formal writing.

How do I check which form to use?

Read the whole sentence. If not negates the ability itself, use cannot. If not belongs with a following phrase or verb, keep not separate or rephrase.

What about "can not only" vs "cannot only"?

Write "can not only" because not pairs with only. "Cannot only" would imply impossibility in a different way and is rarely what you mean.

Will spellcheck catch this?

Sometimes, but not always. Spellcheck flags uncommon phrases, but sentence-level checks or a quick manual read are the most reliable methods.

Check the whole sentence before you send it

A single-word choice can change meaning. Read the sentence aloud or use an editor tool (the widget above) to confirm that not attaches to the right word and that cannot vs can not communicates your intended meaning.