Cannot, Can Not or Can't—Which Should I Use?

Can’t? Cannot? Can not? Find out the right way to use all three.

Can’t is a contraction of cannot, and as such it’s sometimes unsuitable for formal writing. In everyday writing and in speaking, it’s ubiquitous:

I can’t go out until I proofread my paper.

Peter can’t believe what’s happening in front of his eyes.

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Cannot is better for formal writing:

I cannot wait until Friday to get the report.

We cannot allow these obstacles to slow us down.

Don’t use can not when you mean cannot. The only time you’re likely to see can not written as separate words is when the word “can” happens to precede some other phrase that happens to start with “not”:

We can not only break even, but also turn a profit.

The company’s new product can not only reduce emissions, but also trap some of the existing greenhouse gasses.

Here is a quick summary:

Can’t is a contraction of cannot, and it’s best suited for informal writing.
In formal writing and where contractions are frowned upon, use cannot.
It is possible to write can not, but you generally find it only as part of some other construction, such as “not only . . . but also.”

Examples

The 30-year-old now says she’s recovering, but there are still days when she can’t drag herself out of bed for her part-time job at a university.

Bloomberg

Jose Mourinho has warned Anthony Martial he cannot keep wasting opportunities given the intense competition in his position after the struggling Manchester United forward was dropped from the squad against Feyenoord.

The Daily Telegraph

Even commit to change publicly to encourage accountability. In this way, apologizing can not only repair a relationship, but it can also become a powerful catalyst for your own personal growth.

Harvard Business Review

Cannot and its related forms aren’t the only words in the English language that give you a choice of spelling. Axe is another one of them, as are minuscule and flyer.

Cannot vs. Can Not vs. Can’t—What’s the Difference?

Examples