The normalized sinc function is the Fourier transform of the rectangular function with no scaling. It is used in the concept of reconstructing a continuous bandlimited signal from uniformly spaced samples of that signal.

The sinc function is defined as: sinc(a) = sin(πa)/(πa), however, it is common to see the vague statement: "the sinc function is of the general form: sin(x)/x." In other words, the sinc is a sine wave that decays in amplitude as 1/x.

In mathematics, the delta function can be expressed as the limit of a sequence of functions, including sin⁡(nx)/x. As n approaches infinity, the graph of sin⁡(nx)/x approaches a spike at x=0, which is the essence of the delta function.