Retrograde describes an interval when a planet appears, from an Earth-based viewpoint, to move backward against its usual direction through the zodiac. The planet does not reverse its orbit; the apparent change comes from the shifting geometry of Earth and the other body in motion.
The transition between direct and retrograde apparent motion is called a station. Software can calculate the motion and station times using declared coordinates, time standards, and settings.
Astrology often interprets retrograde periods through themes such as review, repetition, or inward attention. Those meanings are traditions, not evidence that retrograde motion causes mistakes, returns, or personal events. Practical precautions should rest on actual circumstances rather than a planetary label.
A natal retrograde refers to the motion at a birth-chart time. A retrograde transit refers to a moving body’s current or selected-time motion. For the wider factual boundary, see astrology and astronomy.
Sources and further reading
The project methodology, pinned Astronomy Engine JavaScript reference, and official NASA/JPL Horizons documentation support apparent-motion calculations. They do not support claims that retrogrades cause personal events.