Probability, that is, a measure of the probability of uncertain events in an event. For example, if someone throws a coin, if the probability of it facing up is half, it is said that the coin throwing event has a half probability of facing up.

Probability has a strict and complete definition in its mathematical theory. There are two theories about the probability of something happening in an event: 1. TheoreticalProbability: that is, the probability derived from the nature of the event, also known as prior probability. For example, if a coin has two sides, it can be inferred that the probability of its face facing up is half without waiting for the test; For another example, if there are 30 lottery tickets in a lottery box, among which 10 lottery tickets win, it can be inferred that the probability of winning is one-third. Second, empirical probability: that is, the probability that is summed up many times according to actual phenomena. For example, if a coin is thrown 100 times and the number of times it appears face up is 52 times, it means that the probability of throwing a coin face up is 52/100 = 0.52; For another example, if 4,865 babies were born in a county in a certain year, including 2,534 boys, then the probability of boys being born in this county is 2,534/4,865 = 0.52. This probability is also called posterior probability.