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Kronecker delta

In mathematics, the Kronecker delta is a function of two variables, which is 1 if they are equal, and 0 otherwise. It is written as the symbol δij, and treated as a notational shorthand rather than a function.

It is named after mathematician Leopold Kronecker (1823-1891).

It is used in many areas of mathematics. For example, in linear algebra, the identity matrix can be written as:


See also Levi-Civita symbol.