The Kronecker Delta satisfies the following property:
where and are integers. For a summation:
The elements of the identity matrix can be seen as following Kronecker Delta (i.e, ). To see this, let be an nxn matrix, be its elements and be the nxn identity matrix. Then so,
where the definition of matrix multiplication and the above property of summation was used.
The continuous analogue of Kronecker Delta is Dirac delta.
Weisstein, Eric W. "Kronecker Delta." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/KroneckerDelta.html