‘Cannot' vs 'Can Not': What's the Difference?

By Carly Forsaith, updated on December 20, 2022

'Cannot' vs 'can not': do they mean the same? And if not, which one should you use and when? That's what we'll cover today.

In short, 'cannot' and 'can not' are synonymous, but 'can not' can be ambiguous. Furthermore, 'can not' can be used in some contexts where 'cannot' can't.

What is the Difference Between 'Cannot' vs 'Can Not'?

'Cannot' and 'can not' bear very similar meanings. So what exactly differentiates them?

It depends on the context.

Most of the time, they're just different ways of spelling the same word. 'Cannot' is technically a contraction of the auxiliary verb 'can not,' just like 'can't.' What makes it particularly strange is that there's no such contraction for other auxiliary verbs, like the following:

While they all use the apostrophe contraction ('can't,' 'don't,' 'won't,' 'isn't,' 'haven't'), 'can not' is the only one that has joined both words to make one.

So can you use them both interchangeably? Technically, yes. But using 'can not' can sometimes be ambiguous because it can make it sound like you're saying you have the possibility of not doing something.

Furthermore, there is one instance where you can use 'can not' but not 'cannot': when 'can' is part of one phrase and 'not' is part of another.

Confused? Read on, and I'll explain further.

When to Use 'Cannot'

So how to know when you should use 'cannot' vs 'can not'?

'Cannot' is the negative form of 'can' and is an auxiliary verb, which means it assists the sentence's main verb.

It's used to express the inability or impossibility of doing something. Here are some examples:

I cannot believe he's already back at work after his accident.

She cannot get public transport to school as the buses are on strike.

You cannot have dessert until you've eaten your vegetables.

When to Use 'Can Not'

As I've already mentioned, you can use 'can not' in the same way you would use 'cannot.' Several reputable dictionaries define them as synonymous, such as the Oxford English Dictionary, Merriam-Webster, and Cambridge Dictionary.

So you're free to use 'can not' in the same way as you would use 'cannot.' However, bear in mind that your sentence could be misconstrued as meaning that you could decide not to do something. For example:

I can not wait until my holiday.

This sentence could mean that you are impatient for your holiday to begin. But it could also mean you are considering not waiting for your holiday. Let's extend this sentence to show you what I mean:

I can not wait until my holiday and just go now.

It's unlikely that your interlocutor will think this is what you meant, but it's best to be safe than sorry, which is why I recommend using 'cannot' in circumstances like this.

There is; however, a time 'can not' is appropriate and 'cannot' isn't. That is when the two words are two different parts of the sentence. For example:

I believe we can not only open on time, but it will also be a raging success.

In the sentence above, you're stating that two things are true. The key expression here is 'not only.' So 'can' is part of the phrase "I believe we can," and 'not' is part of the phrase "not only open on time."

Concluding Thoughts on 'Cannot' vs 'Can Not'

I hope this article has helped clarify the difference between 'cannot' and 'can't' for you and that you feel comfortable using both.

In summary, I recommend using 'cannot' (or even 'can't' in informal settings) when you want to express the inability or impossibility of something happening. Save 'can not' for contexts where you use the expression 'not only.'

To learn more important grammar concepts, head to our blog, which covers the most commonly confused words and expressions.

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Written By:
Carly Forsaith
Carly Forsaith is one of the lead freelance writers for WritingTips.org. Carly is a copywriter who has been writing about the English language for over 3 years. Before that, she was a teacher in Thailand, helping people learn English as a second language. She is a total grammar nerd and spends her time spotting language errors on signs and on the internet.

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