Although they generally move in the same direction along a path across the sky (the ecliptic), individual planets sometimes reverse their direction briefly, exhibiting retrograde motion.
雖然它們通常沿著一條路徑循著同樣方向從天空的這一端移動到那一端（請參閱黃道），但是某些獨特的行星有時候會短暫地逆轉其移動方向，顯示出逆行運動。