Multidimensional transform
In mathematical analysis and applications, multidimensional transforms are used to analyze the frequency content of signals in a domain of two or more dimensions. == Multidimensional Fourier transform == One of the more popular multidimensional transforms is the Fourier transform, which converts a signal from a time/space domain representation to a frequency domain representation.
Source: Wikipedia — Multidimensional transform (CC BY-SA 4.0)