Dictionary.net

Given a position operator P(i,j), let A be a nxnmatrix whose element A[i][j] is the number of times thatpoints with grey level (intensity) g[i] occur, in the positionspecified by P, relative to points with grey level g[j]. LetC be the nxn matrix that is produced by dividing A with thetotal number of point pairs that satisfy P. C[i][j] is ameasure of the joint probability that a pair of pointssatisfying P will have values g[i], g[j]. C is called acooccurrence matrix defined by P. Examples for the operator Pare: "i above j", "i one position to the right and two belowj", etc.