When to use cannot vs. can not – Microsoft 365

Cannot versus can not: what’s the difference?

“Cannot” is a compound word, formed by merging “can” and “not.” It’s the preferred and widely accepted version in contemporary writing. In formal writing, such as academic papers, reports, or business communications, “cannot” remains the norm, offering a clean, concise expression of impossibility or inability:

• I cannot attend the meeting tomorrow.
• The CEO regrets to inform the staff that they cannot offer bonuses this year.

On the other hand, “can not” is a two-word formation, where “can” and “not” are distinctly separate. It’s employed when you want to emphasize the negation, separating “can” and “not” for added emphasis or clarity—especially on the written page:

• I absolutely mean it when I can not eat any more dessert.
• You can not go out to the party tonight!

In formal writing, such as academic papers, reports, or business communications, “cannot” remains the norm. It offers a clean, concise expression of inability or prohibition without any confusion. Conversely, in creative writing, dialogue, or when emphasizing a unique context or contrast, “can not” can be used to drive home a specific point or to showcase the additional capabilities despite an initial negation.

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However, both cannot and can not also readily lend themselves to the common contraction “can’t.” This is the most casual usage of the form, and by far the most popular:

• Steve called to say that he can’t make it to the basketball game.
• Sammy Hagar famously sang “I can’t drive 55” in protest of speed limits.

“In formal writing, such as academic papers, reports, or business communications, “cannot” remains the norm. It offers a clean, concise expression of inability or prohibition without any confusion.”

”Can not” as a correlative

“Can not” also has a common alternate use: it forms a correlative conjunction. You may remember that correlative conjunctions are two-part connectors that join sentence elements of equal importance. Here, the two words “can not” are commonly combined with the “not only…but also” construction. This is a key differentiator of the “cannot” vs. “can not” debate, as evident in the following examples:

• I can not only sing but also dance.
• These funds can not only budget for libraries, but also schools.

Remember, consistency is key in writing. Whichever you choose, maintain uniformity throughout your text to ensure clarity and coherence. “Cannot” offers simplicity and conventionality, suitable for most situations, while “can not” provides emphasis or contrast in specific contexts—as well as its use in correlatives. Finally, “can’t” voices a different sentiment in your text or writing. For more tips on how to write accurately, learn the difference between “lightening” and “lightning,” understand gerund phrases and how they work, or brush up on popular tenses.