A portion of an array containing more than one element is called an array section. Often an array operation is needed on an array section, not the entire array. The earlier example of normalizing the pivot row of a matrix is a case in point. In this example it was exactly one row of the matrix that was of interest in the computation, not the whole array. In this case the array section is one row of a two-dimensional array; in general virtually any rectilinear subset of an array can be an array section and hence an object that can be used in array operations. An array section may be of any dimensionality up to and including the dimensionality of the array on which the section is being defined.