Speed is displacement (distance traveled) per unit time. Velocity is displacement (distance traveled) per unit time in a given direction. The directionality associated with velocity makes it a vector quantity, while speed is a scalar quantity. The main difference between them in everyday life is that speed is usually used. properly, but velocity is usually used Im properly. -- 30 miles per hour is a speed. -- 30 miles per hour north is a velocity. -- 30 miles per hour north and 30 miles per hour west are the same speed but different velocities.