What does a red octagonal (eight-sided) sign always mean?

A red octagon (eight-sided shape) is always a STOP sign. It is the only sign with this shape, so it can be recognized even from the back or when partially obscured. At a stop sign, the driver must come to a complete stop at the marked stop line, crosswalk, or before entering the intersection, then yield to traffic and pedestrians before proceeding. The unique shape-and-color coding of traffic signs lets drivers identify them quickly: the octagon is reserved exclusively for STOP. Recognizing standard sign shapes and colors, like the red octagon, is core road-sign knowledge.