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Is “Cannot” One Word or Two?

In English, compound words and contractions can sometimes be confusing. There are some words where it’s not apparent if you should write them as one or two words and if that could change their meaning. Many English speakers wonder if “cannot” is one word or two.

Most English speakers prefer “cannot” over “can not,” though it is acceptable to write both “cannot” and “can not” to express the negative form of “can.” In informal speech and writing, the shorter contraction “can’t” often replaces “cannot.”

This article will explore the meaning of “cannot,” its origins, and how we can use it in everyday speech. We’ll also explore contractions such as “can’t” and understand when we should and shouldn’t use them.

What Does “Cannot” Mean?

“Cannot” is the negative form of the verb “can.” If I “cannot” do something, then I am saying that I am unable to do that thing. We use “cannot” to express inability or incapacity, as in “I cannot come to lunch today” (source).

In American English, it’s equally acceptable but less common to say, “I can not come to lunch today,” and the meaning is unchanged. Interestingly, in British English, only “cannot” is used, and we only see “can not” written separately in a sentence when the “not” is part of another phrase. 

The word “cannot” dates back to Old English and has been in everyday use since the 1400s (source). It’s the negative form of the verb “can,” which means to be able to. The contraction “can’t” has been used since the early 1700s. 

How Do You Use “Cannot”?

We use “cannot” as an auxiliary verb, which means it behaves as a helping verb to assist the main verb in the sentence. “Cannot” expresses ability or permission, and we always follow it with another verb – unless the verb is inferred (source). 

As a modal auxiliary verb, “cannot” expresses possibility or necessity (source). Consider the sentences below, which demonstrate how we use “cannot.”

  • I cannot eat this because I’m allergic to wheat.
  • We have agreed that the students cannot attend tonight’s party.
  • She cannot be serious in suggesting that I sing at the concert.

These sentences illustrate how we use “cannot” to help another verb. In the examples above, we use “cannot” together with the main verbs of “eat,” “attend,” and “be.”

Modal verbs modify grammatical mood. This means that they show the possibility or the likelihood of something happening. The verb “can” communicates mood, and “cannot” negates that because it is in the negative form. It, therefore, expresses something impossible or not to be (source). 

When Can You Use “Cannot”?

We use “cannot” any time we want to say that we are unable to do something. We use “cannot” in the present tense to describe that we don’t have the ability or permission to do something.

As modal verbs, “can” and “cannot” do not have all the tenses that other verbs have. In the simple past tense, we use “could not” and on the rare occasions when we need to use a past participle, we use “not be able to.” 

Consider the examples below that illustrate the use of “cannot” in various tenses.

PresentI have tried, but I cannot eat peas.
PastI had tried, but I could not eat peas.
FutureI will try, but I will not be able to eat peas.
PresentShe failed the course and therefore cannot graduate.
PastShe failed the course and therefore could not graduate.
FutureShe failed the course and, thus, will not be able to graduate.

In What Context Can You Use “Cannot”?

We use “cannot” anytime we want to say the opposite of “can.” It’s a widely used verb and can be used in almost any situation and setting when we are speaking in the negative form. 

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You’ll often hear “cannot” used in conversation when people are discussing their plans or actions. Sometimes, you may find “cannot” used on its own because we imply the verb it is helping, as illustrated in the exchange below.

  • Speaker 1: Are you able to pick Jack up from the airport on Tuesday?
  • Speaker 2: I’m sorry. I cannot.

Here, Speaker 2 is saying, “I cannot pick Jack up from the airport on Tuesday.” The speaker implied the latter part of the sentence due to the question preceding it. English speakers often do this to avoid sounding repetitive.

When Not to Use “Cannot”

Most of the time, “cannot” is the correct form to choose. However, in a casual setting, you’re better off selecting the informal contraction “can’t.” Also, if you mean to say that you are able or willing to do something, you should use “can” rather than “cannot.”

There are also a few specific times when it’s not appropriate to use “cannot.”

When Not is Part of Another Phrase

Sometimes, you have to use “can not” rather than “cannot” because “can” and “not” form part of two different phrases (source). This is most common in the correlative construction “not only… but….” Correlative constructions link two elements of a sentence together. 

In cases like this, “not” is part of another construction, and you, therefore, have to use two words, as shown in the examples below. 

  • My dog can not only catch a ball but also lie down on command.
  • Jane can not only speak French, but German too.
  • The baby is trying to walk, but she can not yet do so unaided.

In these examples, “not” is part of a separate construction – in this case, “not only” and “not yet.” We must, therefore, separate the two words to avoid confusion. Because they sound slightly awkward, most often, it’s just easier to rephrase your sentence and avoid confusion, as shown below.

  • My dog can catch a ball and also lie down on command.
  • Jane can speak both French and German.
  • The baby is trying to walk but still needs assistance.

For Emphasis

Another time when we could choose to split “cannot” into “can not” is when we want to emphasize the “not” part of the expression. Consider the examples below, where we use the two words separately to emphasize “not.”

  • I absolutely can not do it!
  • You can not be serious!
  • I can not believe that’s what you think!

In these examples, we could easily use “can’t” or “cannot,” which wouldn’t fundamentally change the meaning. However, by separating it into two words, we place more emphasis on the negative sentiment of the sentence. These sentences also end with an exclamation point, which helps to illustrate that they are spoken emphatically. 

What Can You Use Instead of “Cannot”?

We’ve already established that you can use either “can not” or “can’t” as alternatives to “cannot.” Additionally, there are other ways of expressing the same sentiment.

The list below includes several common alternatives for “cannot”:

  • Be unable to
  • Be unwilling to
  • Be incapable of 
  • Can’t
  • Can not

In the sentences below, we show how we use these alternatives. In all cases, “cannot” could be substituted for the synonym.

  • I am unable to assist with the bake sale because I’m in meetings all day. 
  • I cannot assist with the bake sale because I’m in meetings all day.
  • Jane is unwilling to give her support to this candidate.
  • Jane cannot give her support to this candidate.
  • Most people are incapable of balancing on one leg for a minute.
  • Most people cannot balance on one leg for a minute.
  • I’m too sick – I can’t go to school today. 
  • I’m too sick – I cannot go to school today. 
  • She can not be serious about leaving Mary behind.
  • She cannot be serious about leaving Mary behind.

The contraction “can’t” is most commonly used instead of “cannot.” However, you should be careful to include the apostrophe. If you write “cant” instead, the word has an entirely different meaning.

You can use this uncommon word as a verb or noun. As a noun, a “cant” is an insincere statement that one cannot trust (source). As a verb, “cant” means to lean or be in a sloping position. It also has several other meanings, but it’s not a word you will come across often. 

Using “Cannot” in a Full Sentence

The most common use of “cannot” is as an auxiliary verb in a present tense sentence. Occasionally it’s used on its own as a response with an implied verb. 

Let’s look at the examples below, which all show how we can use “cannot” in a complete sentence. 

  • It’s far too hot today. I cannot go outdoors.
  • Jane is ill and unfortunately cannot attend the show tonight. 
  • I just cannot understand what led her to behave like that. 
  • (Person 1): Are you able to go with James to the dance?
  • (Person 2): No, I cannot.
  • Jack is really weak. He cannot be our best candidate for president. 

In all these sentences, we could use “can’t” or “can not” instead of “cannot,” and they would be grammatically correct and have the same meaning. 


We use contractions in English, especially in conversation. We create contractions when we join two words together and shorten them. Some of the most common are “can’t,” “it’s,” and “don’t.”

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In conversation, it can sound very stiff and formal if you don’t use contractions. Consider the examples below of common English contractions.

Original Two WordsContraction
I / You / They haveI’ve / You’ve / They’ve
He / She / It isHe’s / She’s / It’s
Can notCan’t
Do notDon’t
Has notHasn’t
Will notWon’t
Does notDoesn’t
He / She / It will He’ll / She’ll / It’ll 
Must haveMust’ve

When we make contractions, we are squashing two words together into a shortened form. Remembering how to spell contractions and where to put the apostrophes can be tricky. It’s helpful to remember that we add apostrophes where we’ve left letters out from the original words (source). 

Let’s think about “can’t.” The original words are “can” and “not.” We’ve joined them together to create “can’t” and have left out the “o” from “not.” That’s why the apostrophe is where it is. Think about “he’ll.” We’ve joined “he” and “will” and left out the “wi” from “will,” so we replace that gap with an apostrophe. 

One exception to this rule is “won’t,” which is a commonly used contraction. It looks a little different because it’s based on 16th-century usage when “woll not” was how people spoke.

Another significant contraction to pay attention to is “it’s.” This contraction is the abbreviation for “it is.” English speakers often confuse “it’s” and “its.” The former is the contraction of it + is. The latter is the possessive form of “it,” as in belonging to “it.” 

Contractions in Writing

Because we often use contractions when speaking, it’s not wrong to use them in most writing. In magazines and blogs, contractions reflect the medium’s informal nature. 

The only time you shouldn’t use them is in formal or academic writing. Here, it’s always best to write out the words in their entirety so that your writing expresses the necessary formality (source). 

“Cannot” is a contraction because we’ve combined two words. We haven’t left out any letters in this case, but it’s still considered a contraction.

There are other times in English where we combine two whole words to create a compound word that marries the two words together. To find out more on this topic, read our article Is “Summertime” One Word or Two? 

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Final Thoughts

Whether “cannot” should be one word or two is a topic that has confused many English writers. The answer is that either is acceptable, although it’s rare to see it as two words unless you try to distinguish between two different phrases. It’s safest to use either “cannot” or “can’t,” depending on the context.

It’s also important to remember that although contractions are common in everyday speech, there are times that we need to be more formal, and then it’s better to use “cannot” than “can’t.”