Anomaly

Part of speech: noun (n.)

1. Deviation from the common rule; an irregularity; anything anomalous. We are enabled to unite into a consistent whole the various anomalies and contending principles that are found in the minds and affairs of men. Burke. As Professor Owen has remarked, there is no greater anomaly in nature than a bird that can not fly. Darwin.

2. The angular distance of a planet from its perihelion, as seen from the sun. This is the true anomaly. The eccentric anomaly is a corresponding angle at the center of the elliptic orbit of the planet. The mean anomaly is what the anomaly would be if the planet's angular motion were uniform.

3. The angle measuring apparent irregularities in the motion of a planet.

4. Any deviation from the essential characteristics of a specific type.