What is the Difference Between "Cannot" and "can Not"?

Tricia Christensen
Tricia Christensen

The main difference between “cannot” and “can not” is that the first term deals with impossibility and the second handles choice. The two-word version also is more common when a person wants to add emphasis on something, or when he wants to stress that someone has more than one skill. Mistakes about how to use them properly means that they are virtually interchangeable in regular speech, however.

With a no entry street sign, a vehicle "cannot" enter.
With a no entry street sign, a vehicle "cannot" enter.

Impossibility vs. Choice

One of the most common explanations for the difference between “cannot” and “can not” is that, with the former word, there is no chance someone can carry out an activity, no matter how much he might want to do so. The following sentences both are based on this concept of impossibility:

Someone who is full from eating "can not" eat anything else.
Someone who is full from eating "can not" eat anything else.

Jane cannot jump 50 feet in the air.
We cannot go to Pluto.

In these examples, “cannot” essentially means “lacks the ability to." In the first instance, for example, the way the human body is made and functions always will keep Jane from reaching the extreme height, regardless of her fitness level. The second sentence is true because currently, scientists do not have all the knowledge or technology that a mission to Pluto would require.

By contrast, when a person uses “can not,” the ability to do the action still exists.

Yuri can not study anymore.
Sam can not have a drink.

For both these cases, “can not” translates to “is not going to” or “is opting not to.” In other words, the subject has a choice. Yuri can study, for example, or he can go do something else. Sam can consume a beverage, or he can leave it be.


Typically, a contraction represents the joining of more than one word, usually as a way to make speech shorter and more efficient. Contractions also can eliminate syllables within words, however, sometimes for a poetic purpose, such as sticking to a particular meter. A good example is “e’er,” a shortened form of “ever” pronounced like the words “air” or “heir.” Most experts say that the contraction “can’t” functions in this way and, therefore, is a shortened version of “cannot” rather than a joining of “can” and “not.”

With the contraction representing “cannot,” technically, someone only should use it when they really mean that the subject of their sentence does not have the ability to do something. In common speech, however, people frequently use it incorrectly. A person might say, "I can't cook tonight," for example.


The word “cannot” rarely needs to receive emphasis because the meaning is not ambiguous — it always means that it isn’t possible for the subject to complete the action. The phrase “can not,” however, deals with options, and people can stress what they want to happen or are going to pick. A father upset about his daughter’s short skirt, for instance, might say, “You can not wear that out of this house, young lady!” He essentially would be stressing that, even though she’s physically capable of donning the offensive clothing and going somewhere in it, he’s not going to let her, making her choice for her. In the same way, when a person says “You can not be serious,” he really means, “You are choosing not to be serious,” which is a roundabout way of expressing disbelief or disapproval and saying he wants the other person to quit fooling around.

Multiple Abilities

Related to the idea of emphasis is the concept of stressing that someone has multiple abilities. People usually do this using “not only…but” statements, such as “He can not only sing, but he acts, too.” A person generally can rewrite a sentence like this to make the dual abilities a little more clear, such as “He can sing, and he can act, too.” The first construction, however, draws a little more attention to the second ability, essentially saying, “Yes, he has Ability A, but don’t ignore Ability B.”


Even though these two terms technically do have slightly different meanings, widespread inappropriate application has made them almost interchangeable in everyday language. According to some sources, though, “cannot” is the more common version. Location has some influence on usage, with some areas preferring the single word and others preferring the phrase.

Tricia Christensen
Tricia Christensen

Tricia has a Literature degree from Sonoma State University and has been a frequent wiseGEEK contributor for many years. She is especially passionate about reading and writing, although her other interests include medicine, art, film, history, politics, ethics, and religion. Tricia lives in Northern California and is currently working on her first novel.

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Discussion Comments


This pseudo-scientific explanation is pure nonsense. Not a single native speaker of English would agree that "Sam can not have drink" may mean that he has chosen not to have a drink. Certainly the writer got all the attention he/she so badly wanted.


The examples given above are the difference between 'can/ability' and 'can/permission' which is also expressed as 'may.' That might be a clearer way of describing the difference in usage.


It is useful to know the small details of any language's grammar especially the one you prefer to speak with. For me, I liked that and I now can tell the difference between can not and cannot and use them in right way as well. --Almaleki H


I share your sentiments, "plaid". I also agree with "pimiento", however Anonymous #5 gets the cowbell. He or she is right on the money. "Most students can't stand the students who can not study and still make the grade."


I did not exactly agree with this explanation. Separating the two creates an instance of "being able to not do something," as in "You can not know someone well and still seek their advice." The counter example, "You cannot know someone well after merely seeking their advice one time."


Gee. Now I can't seem to get rid of this headache I got from reading about the difference between using cannot and can not!


Presently, even in academia, it is considered acceptable to use contractions during formal writing.


@plaid - I know what you mean all too well. Most college professors won't allow you to use contractions in a thesis and especially my English Professor to begin with. The fact that this article mentions that "cannot" is an absolute is a very good way of putting things. When I was reading it, I couldn't even think if I normally use "can not" or "cannot" in most of my writing.


This is a great article and focuses on an aspect of the English language that many people just ignore or avoid entirely. As is says towards the end, many people just use the contraction "can't," but in many aspects of life, like being a professional writer, you would not want to use a contraction.

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