One can also understand the asymmetry term intuitively as follows. It should be dependent on the absolute difference | N − − Z | , and the form ( N − − Z ) 2 is simple and differentiable, which is important for certain applications of the formula. In addition, small differences between Z and N do not have a high energy cost. The A in the denominator reflects the fact that a given difference | N − − Z | is less significant for larger values of A.