Triple correlation
The triple correlation of an ordinary function on the real line is the integral of the product of that function with two independently shifted copies of itself:
![\int_{-\infty}^{\infty} f^{*}(x) f(x+s_1) f(x+s_2) dx](/Images/godic/202502/17/eaba0dc7613ad813a46e90f12059ba4d2749.png")
The Fourier transform of triple correlation is the bispectrum. The triple correlation extends the concept of autocorrelation, which correlates a function with a single shifted copy of itself and thereby enhances its latent periodicities.