(mathematics) a function that changes the position or direction of the axes of a coordinate system WordNet 3.0 & Open English WordNet

In mathematics, a transformation is a function f, usually with some geometrical underpinning, that maps a set X to itself, i.e. f : X → X. Examples include linear transformations of vector spaces and geometric transformations, which include projective transformations, affine transformations, and specific affine transformations, such as rotations, reflections and translations. Wikipedia

Concerning functions from sets to themselves Wikipedia Disambiguation

Concerning functions from sets to themselves. For functions in the broader sense, see function. Wikipedia Disambiguation

The replacement of the variables in an algebraic expression by their values in terms of another set of variables; a mapping of one space onto another or onto itself; a function that changes the position or direction of the axes of a coordinate system. Wiktionary