cannot vs can not

Although they mean the same thing and can be interchangeable, by far the most common is “cannot” and you should probably use it except when you want to be emphatic: “No, you can NOT wash the dog in the washing machine.”  Plus, “cannot” is the modern way of writing “can not”. 🙂


  • Alex Skorkin

    Modern convention and preference use the spelling “cannot.” Most modern word-processing software even highlights the use of “can not” as grammatically incorrect. In addition, specific style guides may give the distinction for this preference as well. When writing for your company, always use “cannot” rather than “can not.”

  • Alex Skorkin

    In general, use cannot whenever you could mentally substitute can’t. Use can not when not goes with another word, such as only:

    He cannot hum. [He can’t hum.]

    She can not only hum; she can play the bagpipes. [She can hum.]

    But beware of times when not doesn’t go with only:

    He cannot only inhale; he must also exhale. [Only here means “solely” rather than “merely.” Our litmus test still works, however: He can’t only inhale.]