Let’s address the most important difference first – Cannot or Can Not?

Does that little space between the two words make any difference at all?

Yes, it does! Let’s see how.

Cannot and Can Not – What’s the Difference?

I am sure you are aware that cannot is the negative form of the verb can. Though writing it as can not is acceptable, the usual way is to write it without the space. Why? Because, can not (with the space) has another use.

Can not is used when the 'not’ is a part of another construction like 'not only’.

For example:

• This new Smartphone can not only capture videos, but also take photos simultaneously.
• This new Smartphone cannot capture videos and photos simultaneously.

Do you see how just one space changed the entire meaning of the sentence? Let’s move on.

Cannot and Can’t – Which to Use When

Can’t is the contraction of cannot. It should be used in informal writing or speaking only – like when you text or chat with your friend or send an email to a colleague you are friends with.

I can’t go shopping today.

I can’t see you at lunch today.

Cannot should be used for formal writing. For instance, for emails to your boss or reports that you make.

I cannot send in the reports today

I cannot come to office today as I am sick.

Keep these minor details in mind as they make major differences!