In
mathematics, the
Kronecker delta or
Kronecker's delta, named after
Leopold Kronecker, is a
function of two
variables, usually just positive
integers. The function is 1 if the variables are equal, and 0 otherwise:
where the Kronecker delta d
ij is a
piecewise function of variables
i and
j. For example, d
1 2 = 0, whereas d
3 3 = 1.