cannot, can not, can’t

The negative of the auxiliary can, cannot occurs less frequently than the contraction can’t but much more frequently than can not, which is sometimes used for emphasis and to reflect the fact that this locution may be stressed on the not as well as on the can. Cannot is Formal, can’t relatively Informal in writing, and can’t is the more frequent in Conversational contexts, but it is often appropriate as well even in some Oratorical uses. All three forms are Standard. Cannot, like can’t, is a very frequent replacement for may not.