Dirac delta
nounEtymology Named after English theoretical physicist Paul Dirac (1902–1984); the notation was chosen because the symbol behaves analogously to the Kronecker delta.
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Mathematics, Sciences A function-like symbol denoted as δ, with the property ∫f(t)δ(x-t)dt=f(x), informally understood as a function with an infinite value at 0 and zero elsewhere, and formally as a distribution or a measure.