The Kronecker delta is defined as having value 1 when and 0 otherwise ( and are integers). It may also be written as
or
. It is a special case of the generalized Kronecker delta symbol.
The delta symbol was first used in print by Kronecker in 1868[1].
Example.
The
identity matrix can be written in terms of the Kronecker delta as simply the matrix of the delta,
, or simply
.