In mathematics, a transformation, transform, or self-map[1] is a function f, usually with some geometrical underpinning, that maps a set X to itself, i.e. f: X → X.[2][3][4] 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.[5][6]