The mathematical theory of the formation and behavior of queues or waiting lines. The name is also applied loosely to the mathematical study of a wide variety of problems connected with traffic congestion and storage systems. Uneven flow through a service point, with fluctuating arrivals and service times, constitutes a major topic of operations research, and some current work in queueing theory goes under that title. For the mathematician, queueing theory is particularly interesting because it is concerned with relatively simple stochastic processes, which are in general nonmarkovian and possibly stationary.