"The Gittins index is a measure of the reward that can be achieved by a random process bearing a termination state and evolving from its present state onward, under the option of terminating the said process at every later stage with the accrual of the probabilistic expected reward from that stage up to the attainment of its termination state. It is a real scalar value associated to the state of a stochastic process with a reward function and a probability of termination."@en .