\begin{definition}[Definition:Prisoner's Dilemma]
The '''Prisoner's Dilemma''' is an instance of a class of games whose mechanics are as follows:
Two suspects in a crime are interviewed separately.
If they both confess, they will be sentenced to $3$ years in prison.
If only one of them confesses, he will be freed and used as a witness against the other, who will then receive a sentence of $4$ years.
If neither one confesses, they will both be sentenced for lesser crime, and each will spend $1$ year in prison.
\end{definition}