An operation which relates a function to its derivative or to its differential. The derivative or the differential being considered may be defined at a point or on some set, or else partial derivatives, directional derivatives, partial and total differentials may be considered, while the functions themselves need not necessarily be numerical, but may be functions of a more general nature.
Differentiation. G.P. Tolstov (originator), Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Differentiation&oldid=18122