Which root means "backwards"?

The root that means "backwards" is derived from Latin, where "retro" specifically indicates a reverse or backward direction. This root is commonly used in various terms, such as "retrograde," which means moving backward in time or position, and "retrospective," referring to looking back on past events.

In contrast, the other roots do not pertain to the concept of moving backward. "Sarco" relates to flesh or muscle, "pneumo" pertains to air or lungs, and "phobia" refers to an irrational fear. Therefore, "retro" stands out as the only root that accurately conveys the meaning of "backwards."