[re.frac.tion] n (1603) 1: deflection from a straight path undergone by a light ray or energy wave in passing obliquely from one medium (as air) into another (as glass) in which its velocity is different
2: the change in the apparent position of a celestial body due to bending of the light rays emanating from it as they pass through the atmosphere; also: the correction to be applied to the apparent position of a body because of this bending
3: the action of distorting an image by viewing through a medium; also: an instance of this