cannot

1. 1
   not ableverb

   To be unable to do something; the negative form of can, placed before the base form of another verb.

   He cannot remember where he parked the car.

   The committee cannot reach a decision without more data.

   UsageFollowed by the base verb with no to: cannot swim. Usually written as one word; can't is the everyday spoken form.

   Note

   Can and not fused into a single word, and the fused form is the ordinary written negative of the modal. Here the barrier is ability or circumstance. In "I cannot open the window. It is stuck," the second sentence names what is in the way. The same spelling can also forbid, as in the "not permitted" meaning, and a stated reason like this one is often what tells the reader which is meant. Source

   Checked 5 Nov 2026 · 1 fact

   • Cannot was formed by joining can and not. en.wiktionary.org
2. 2
   not allowedverb

   To be forbidden or not permitted to do something, often because of a rule, law, or authority.

   Visitors cannot enter the lab without a security badge.

   Under the new policy, employees cannot accept gifts from vendors.

   UsageCommon in rules, often with a passive: cannot be used, cannot be patented. A passive can also mean impossible: cannot be repaired.

   Note

   Rules and rulings speak in this sense. Karen McVeigh's Guardian report of 2013 says that natural human genes cannot be patented, and in that sentence no one's ability is in question, only what the law allows.

3. 3
   certainly notverb

   Used when the speaker feels certain that something is untrue, impossible, or did not happen.

   These sales figures cannot be right; the store never sells that many shirts in one day.

   She cannot have seen my email yet, or she would have answered by now.

   UsageFor the past, cannot have + past participle: cannot have seen. In speech can't is usual: that can't be right.

   Note

   Here nobody lacks the ability or the permission: the speaker is ruling something out, much as must rules something in (it must be him; it cannot be him).

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