Retrograde motion

Retrograde motion is the apparent movement of a planet that, seen from Earth, seems to move backward through the zodiac for a while. It is an optical effect caused by the relative speeds of the orbits: no planet actually reverses direction. The Sun and Moon are never retrograde. In astrology, a retrograde planet is read as an energy turned inward or toward revision; Mercury retrograde is reputed to bring misunderstandings and delays.