used the Wiener process to model price changes on the Paris Bourse, while A. K. Erlang used the Poisson process to model the number of phone calls occurring in a given period of time. These two processes are widely treated as central to the theory of stochastic processes, and they were invented repeatedly and independently, both before and after Bachelier and Erlang, in different settings and countries.

The term random function is also used to refer to