Define event in probability.

An event in probability is a set of outcomes of an experiment.

In probability theory, an event is a subset of the sample space, which is the set of all possible outcomes of an experiment. For example, if we toss a coin, the sample space is {heads, tails}. An event could be the subset {heads}, which represents the outcome of getting heads on the coin toss. Another event could be the subset {heads, tails}, which represents the outcome of getting either heads or tails on the coin toss.

Events can be classified as simple or compound. A simple event is an event that consists of a single outcome, while a compound event is an event that consists of more than one outcome. For example, in the coin toss example, the event {heads} is a simple event, while the event {heads, tails} is a compound event.

Events can also be mutually exclusive or independent. Mutually exclusive events are events that cannot occur at the same time, while independent events are events that do not affect each other's probability of occurring. For example, if we roll a die, the events {rolling a 1} and {rolling a 2} are mutually exclusive, while the events {rolling an odd number} and {rolling a number greater than 3} are independent.

In summary, an event in probability is a set of outcomes of an experiment, which can be simple or compound, mutually exclusive or independent.