Probability is the chance that something will happen, but it is not 100% sure. It is that something is probable. It may not happen but there is a chance. Probability is sometimes based on luck, but in mathematics there is a way to figure it out. Chance however, is something that happens unpredictably without discernible human intention or observable cause. There is no way to find out the chance of something happening. For example, there is achance I will win the lottery, but most of the time you can never figure out if you will win or not.