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The primordial trispectrum is the connected four-point function with its momentum-conserving delta function removed. Exchange diagrams split naturally into $s$, $t$, and $u$ channels according to which pair of external momenta meets at one cubic vertex.

A trispectrum is a Fourier-space connected fourth-order statistic; this entry applies it to primordial cosmological perturbations.

The trispectrum is the Fourier transform of a fourth-order cumulant, a fourth-order counterpart of the bispectrum. It describes connected four-point correlations; the primordial trispectrum applies it to cosmological random fields.