Probability is a branch of mathematics that deals with the study of random events and the likelihood of their occurrence. It involves the calculation of the chances or likelihood of a particular event occurring, based on the available information and assumptions.

Probability is often expressed as a number between 0 and 1, with 0 meaning that the event is impossible and 1 meaning that the event is certain to occur. For example, the probability of flipping a coin and getting heads is 0.5 or 50%, assuming the coin is fair.

There are different methods for calculating probability, including the classical method, the empirical method, and the subjective method. Probability theory is widely used in various fields, including statistics, economics, engineering, and physics, to name a few.