Can't vs. Cannot What's the Difference? Can't and cannot are both contractions of the phrase " cannot ," but they are used in slightly different contexts. "Can't" is more informal and commonly used in spoken language, while " cannot " is more formal and often used in written communication. CANNOT definition: 1. the negative form of the verb "can": 2. used to say that something will certainly happen: 3…. Learn more. When should you use the words " cannot " and "can't"? And is " can not " ever written as two words? Check out our blog post to find out. Cannot or Can Not – Created by 7ESL Cannot or Can Not | Definition, Usage Cannot : Meaning: It is the more common and preferred form of negating “can.” It indicates that something is impossible or not allowed. Use: “ Cannot ” is a single word and is typically used in most cases where you need to express inability or prohibition. Examples: “I cannot attend the meeting tomorrow.” “You cannot park here.” Explanation: “ Cannot ” is the standard, more frequent form, used to show ...