What is the negative of can?

The negative of can is “cannot” and “can’t” which is the contracted form we use mostly when speaking. Both are used in written and spoken English for reference to present tense and can also be used for future tense and the past tense negative of can is “could not” and “couldn’t”.

You will learn the differences of each and how they work with different tenses and when speaking and writing formally and informally.

Can’t is the contracted form of cannot which means it is the shorter and faster way of saying cannot.

However, even though it is shorter and faster they can often have different meanings or emphasis behind their use.

cannot example

As can’t became the popular version of cannot in everyday use it has lost most of its formality and weight. That is why the lesser spoken cannot is used more formally to emphasise the negative which the listener knows the speaker is being serious and not casual.

When spoken, the vocal stress can be put on cannot to emphasis it and make the expression sound more significant and important.


“I cannot believe you did that!” The more stress you put on the word cannot the stronger you convey the feeling of astonishment or disapproval. Compared to “I can’t believe you did that” which doesn’t feel as strong or important.

What tenses are can’t and cannot used?

Can’t and cannot are mostly used for the present simple tense but they can be used for future tense sentences with the help of future references eg. “I can’t play tomorrow”, using the word tomorrow makes the sentence future tense.

Future Tense

To correctly use the future tense for the same meaning you replace “can’t” with “will not be able to” or “won’t be able to”, the contracted form.

Present: “I can’t play.” Future: “I will not be able to play”

Past Tense

When in the past tense you use couldn’t or could not to replace can’t and cannot.

We couldn’t see them.” – Talking about the past.

Have a look at the examples in the table to see how they are used:

TenseExample with “can’t”Example with “cannot”
PresentI can’t swim.She cannot come to the phone right now.
Future (1)You can’t go there tomorrow.He cannot join us next week.
Future (2)You won’t be able to go.He will not join us.
PastI couldn’t swim when I was younger.(uses “could not” for past abilities)
Present PerfectI can’t have eaten that.He cannot have said that.

Here’s a brief explanation for each:

  • Present: Direct statements about current abilities or permissions.
  • Future: Statements about what will not be possible or allowed.
  • Past: “Can’t” and “cannot” are typically used with “could not” to express past inability or impossibility because “can” does not have its own past form.
  • Present Perfect: Used to deny past actions continuing to the present or to express disbelief about them.

How do you use Cannot in a sentence?

It is used to express and highlight inability, prohibition, or the logical impossibility of an action. It cannot be used at the start of a sentence but it can be used at the start of a question.


Example SentenceDescriptionNote on Use
“John cannot come to the meeting.”Statement of InabilitySimple declarative sentence.
“They cannot understand the instructions.”Statement of InabilitySimple declarative sentence.
“The machine cannot operate without power.”Conditional InabilityDemonstrates dependence on a condition.
“There are times when I cannot help but laugh.”Inevitable ActionIndicates actions that are uncontrollable at times.
Cannot she do it by herself?”Formal QuestionInverted question format, more formal.
Cannot the company handle this issue?”Formal QuestionInverted question format, used for emphasis.
“Who cannot join us for dinner tonight?”Question about InabilityDirect question format focusing on inability.
“Where cannot they go during the night?”Question about Prohibition/RestrictionsUncommon construction, focuses on restrictions.

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