Probability
Probability is the part of mathematics. It is to do with chance, the study of things that might happen but might not happen. For example, using probability, you can show that if you throw the coin up in the air and let it land, half of the time it will land with one side facing up, and half the time with the other side facing up. Many coins have the picture of the face of the famous person on one side, and something else on the other side. Often people call the side with the face "heads", and the other side "tails".