A deterministic function returns the exact same value each time it is given the same inputs. What is the value of 3 times 4 (in base 10 arithmetic)? Whether last year or next year, whether in Barbados or on the Moon, whether by human or by computer, the answer is 12. By contrast a stochastic function does not return the same value when given supposedly identical conditions. If I roll this cubical die, what value will appear? Even if I do it, in one setting in the same location, trying my best to be repeatable, the answer is a 1 or a 2 or a … or a 6. This stochastic function returns one of 6 values with an equal probability. It does not consistently return the same value.