Function: noun
Date: 1923
: any of various functions (as F(u) ) that under suitable conditions can be obtained from given functions (as f(x) ) by multiplying by e iux and integrating over all values of x and that in scientific instrumentation describe the dependence of the average of a series of measurements (as of a spectrum) on a quantity of interest (as brightness) especially of a very small magnitude ― called also Fourier transformation