Abberation is an ANOMALY, which is defined as something that deviates from what is standard, normal, or expected. It is often used to describe a deviation from the typical form, structure, or behavior of something. Abberation can also refer to an optical phenomenon caused by the refraction of light through a medium, such as a lens or prism. In this case, it is usually used to describe an aberration in vision, such as astigmatism.