In mathematics, a dilation with center O and nonzero scale factor k maps any point P to a point P' determined as follows:

(1) If k > , P' lies on ray OP and OP' = k * OP.
(2) If k < 0, P' lies on the ray opposite ray OP and OP' = |k| * OP.
(3) The center O is it's own image.
If |k| > 1, the dilation is an expansion.
If |k| < 1, the dilation is a contraction.