To cancel means to officially call off or stop something that was planned. When a baseball game gets cancelled because of rain, it won't happen that day. When you cancel a doctor's appointment, you're telling them you won't be coming. Schools might cancel classes during a snowstorm.

The word can also mean to mark something so it can't be used again. When you mail a letter, the post office cancels the stamp by printing lines across it, proving it's already been used.

In math, when you cancel numbers or variables in a fraction, you're eliminating matching parts from the top and bottom to simplify the problem. If you have 6/8, you can cancel the common factor of 2 to get 3/4.

Recently, people started using “cancel” differently in phrases like cancel culture. This refers to when groups of people publicly criticize someone (often a celebrity or public figure) for something offensive they said or did, sometimes calling for others to stop supporting that person. It's become a controversial topic because people disagree about when public criticism is fair accountability and when it goes too far.