where x 1 , . . . , x n {\displaystyle x_{1},...,x_{n}} are particular values of X 1 , . . . , X n {\displaystyle X_{1},...,X_{n}} , respectively, P ( x 1 , . . . , x n ) {\displaystyle P(x_{1},...,x_{n})} is the probability of these values occurring together, and P ( x 1 , . . . , x n ) log 2 ⁡ [ P ( x 1 , . . . , x n ) ] {\displaystyle P(x_{1},...,x_{n})\log _{2}[P(x_{1},...,x_{n})]} is defined to be 0 if P ( x 1 , . . . , x n ) = 0 {\displaystyle P(x_{1},...,x_{n})=0} .