Deviation from common rule. An irregularity in the motion of a planet by which it deviates from the aphelion or apogee.
♦ Mean anomaly formerly signified the distance of a planet's mean place from the apogee: it is the angular distance of a planet or comet from perihelion supposing it to have moved with its mean velocity.
♦ True anomaly, the true angular distance of a planet or comet from perihelion. (See excentric anomaly and equated anomaly.)