Kronecker delta

noun, Mathematics
1.
a function of two variables, i and j, which equals 1 when the variables have the same value, i = j, and equals 0 when the variables have different values, ij.
Origin
1925-30; named after L. Kronecker
British Dictionary definitions for Kronecker delta

Kronecker delta

/ˈkrɒnɪkə/
noun
1.
(maths) a function of two variables, i and j, that has a value of zero unless i = j, when it has a value of unity δij
Word Origin
named after Leopold Kronecker (1823–91), German mathematician