Source : Free On-Line Dictionary of Computing

cooccurrence matrix
     
         Given a position operator P(i,j), let A be a nxn
        matrix whose element A[i][j] is the number of times that
        points with grey level (intensity) g[i] occur, in the position
        specified by P, relative to points with grey level g[j].  Let
        C be the nxn matrix that is produced by dividing A with the
        total number of point pairs that satisfy P.  C[i][j] is a
        measure of the joint probability that a pair of points
        satisfying P will have values g[i], g[j].  C is called a
        cooccurrence matrix defined by P.  Examples for the operator P
        are: "i above j", "i one position to the right and two below
        j", etc.
     
        (1995-05-11)