aberration

n. 1. A deviation from what is normal or expected. 2. A temporary deviation in behavior by an individual from what is usual for him or her. 3. An astigmatism, dioptric variation, or any other defect of the lens of the eye which brings about a scattering of light so that it does not appropriately project on the retina. 4. A chromatic aberration is one caused when the lens differently refracts different wavelengths of light so that their projection on the retina does not perfectly overlap, causing blurred perception. 5. A spherical aberration is one in which the lens is imperfectly shaped, causing light from different parts of the lens to have different focal lengths, leading to blurred perception.