Cannot or Can Not: What’s the Difference?

English rules surrounding compound words and contractions are not always easy to remember.

Cannot belongs to a certain category of helping verbs and almost always appears as a single word. There are very rare occasions, however, where it is appropriate to have the words separated. Continue reading to find out what they are.

What is the Difference Between Cannot and Can Not?

In this article, I will compare cannot vs. can not. I will use each in a sentence to illustrate the proper context, and I will also reveal a helpful trick to use when you can’t decide whether to use can not or cannot in your own writing.

When to Use Cannot

Definition of can not definition and definition of cannot definitionWhat does cannot mean? Cannot is a contraction of the two words can and not. It functions as an auxiliary verb that describes an action as impossible or not allowed.

Here are some examples,

  • You cannot have any pudding until you eat your meat.
  • You cannot possibly jump far enough to reach the other side of the chasm.
  • But it cannot be easy for Woods to forget how he started 2015: with a first-round withdrawal and three scores in the 80s in his first six events. –The New York Times

On a more technical level, cannot is a negative modal auxiliary verb. Modal verbs, like can, modify grammatical mood; in other words, they reflect a person’s perception of the possibility, likelihood, obligation, or necessity of an action or event.

The verb can communicates the potential mood, which indicates likelihood or possibility. In the contraction cannot, the likelihood or possibility is negated, therefore expressing impossibility or denial.

Is Cannot One Word?

Define can not and define cannotMost readers here probably know the aforementioned information; they understand the meaning of cannot. The primary question at hand is, “Is cannot one word?”

In most cases—say 99 percent of ordinary writing—cannot will appear as a single word. There are only rare circumstances that cannot should appear as two words—and most of these should probably be rewritten anyway (see below for more examples)

Cannot can also be shortened into the contraction can’t, which means the same thing.

For example,

  • You can’t drive faster than the speed limit and expect to avoid getting a ticket.

Remember, however, to avoid contractions in formal writing.

When to Use Can Not

cannot vs can'tWhat does can not mean? Can not, as two separate words, is not a proper verb phrase. When describing an action which is impossible, you should always use cannot.

The words can and not should only appear together when they are part of separate but adjacent phrases.

For example,

  • By buying two cakes, Alina can not only have her cake, but she can also eat it, too.

In this sentence, not is a part of another construction, i.e., not only…but also. In this case, you would separate cannot into two words.

You might also just rework the sentence as a whole.

For example,

  • Since Alina bought two cakes, she can now have her cake and eat it too.

Trick to Remember the Difference

cannot versus can notHere is a trick to remember can not vs. cannot.

A good rule of thumb is that cannot is always one word, never two.

Of course, rules are meant to be broken, and sometimes, albeit rarely, cannot can appear as two words. In these rare cases where it is appropriate, you would be well advised to simply rephrase your sentence, but if you insist on keeping it as it is, just remember that can not must be a part of two separate constructions to be correct.


Is it cannot or can not? These two spellings cause a lot of problems for writers, but the solution is quite simple.

  • Cannot should always be spelled as a single word.
  • Cannot can be further shortened into the contraction can’t.
  • Can not should only be used when not is part of another phrase.

Now that you know the difference between cannot and can not, you don’t need to worry about misusing either of them. Any time you need a reminder, you can reread this article.