Retrograde generally means motion or movement in a direction opposite to the usual or normal direction. It is used in various contexts, including astronomy, biology, and general usage:
- In astronomy, retrograde refers to the motion of a planet or celestial body moving in the opposite direction to the normal rotation or revolution of its primary body (for example, a planet orbiting the Sun or a satellite orbiting a planet). Most planets in our solar system orbit the Sun in a prograde (normal) direction, but some exhibit retrograde motion. This term can also describe the apparent motion of planets as observed from Earth, where they seem to temporarily reverse their path in the sky. This is called "apparent retrograde motion" and happens due to the relative motions of Earth and the other planets in their orbits.
- More generally, retrograde means moving backward or in a reverse direction. This can refer to physical movements, processes (like nerve signals moving opposite to normal flow), or metaphorical uses such as returning to an older, less advanced, or worse state.
- The word "retrograde" comes from Latin roots meaning "backward step."
Thus, retrograde can mean physically moving backward, appearing to move backward due to perspective, or going backward metaphorically or functionally in various contexts. In astronomy, it often refers to orbital or rotational motion opposite the usual direction, or the apparent backward loop of a planet in the sky as viewed from Earth. This summary covers the main meanings and usages of the term "retrograde." Let me know if you want details on a specific context like astronomy or astrology.
