The term retrograde is from the Latin word retrogradus – "backward-step", the affix retro- meaning "backwards" and gradus "step". Retrograde is most commonly an adjective used to describe the path of a planet as it travels through the night sky, with respect to the zodiac, stars, and other bodies of the celestial canopy. In this context, the term refers to planets, as they appear from Earth, to stop briefly and reverse direction at certain times though in reality, of course, we now understand that they perpetually orbit in the same uniform direction.[2]

"Mercury in retrograde" is an example of the term used as a noun for retrograde motion. Retrograde is also sometimes used as an intransitive verb meaning to become, to appear, to behave—or appear to move—in a retrograde fashion.

Although planets can sometimes be mistaken for stars as one observes the night sky, the planets actually change position from night to night in relation to the stars.