In mathematics, the convolution theorem states that under suitable conditions the Fourier transform of a convolution is the pointwise product of Fourier transforms. In other words, convolution in one domain (e.g., time domain) equals point-wise multiplication in the other domain (e.g., frequency domain). Versions of the convolution theorem are true for various Fourier-related transforms. Let {displaystyle f} f and {displaystyle g} g be two functions with convolution {displaystyle f*g} f*g . (Note that the asterisk denotes convolution in this context, and not multiplication. The tensor product symbol {displaystyle otimes } otimes is sometimes used instead.) Let {displaystyle {mathcal {F}}} mathcal{F} denote the Fourier transform operator, so {displaystyle {mathcal {F}}{f}} mathcal{F}{f} and {displaystyle {mathcal {F}}{g}} mathcal{F}{g} are the Fourier transforms of {displaystyle f} f and {displaystyle g} g, respectively