Branching process
In probability theory, a branching process is a type of mathematical object known as a stochastic process, which consists of collections of random variables indexed by some set, usually natural or non-negative real numbers. The original purpose of branching processes was to serve as a mathematical model of a population in which each individual in generation n {\displaystyle n} produces some random number of individuals in generation n + 1 {\displaystyle n+1} , according, in the simplest case, to a fixed probability distribution that does not vary from individual to individual.