In non-scientific language, “speed” and “velocity” mean the same thing. “Velocity” is more formal, “speed” is less formal. “Speed” is used more than “velocity.” But in physics, they are different because in physics “velocity” means “speed in a certain direction”; an object can change “velocity” by changing direction, even if the speed does not change.

These are two notions of physics. The speed describes how fast an object is moving. So a fast-moving object has a high speed and covers a relatively large distance in a short amount of time. Contrast this to a slow-moving object that has a low speed; it covers a relatively small amount of distance in the same amount of time. An object with no movement at all has a zero speed. On the other hand, the velocity is just the speed with a direction meaning that it describes the rate at which an object changes its position. Imagine a person moving rapidly (fast speed) - one step forward and one step back - always returning to the original starting position. While this might result in a frenzy of activity, it would result in a zero velocity. Because the person always returns to the original position, the motion would never result in a change in position. Since velocity is defined as the rate at which the position changes, this motion results in zero velocity.

These are two notions of physics. The speed describes how fast an object is moving. So a fast-moving object has a high speed and covers a relatively large distance in a short amount of time. Contrast this to a slow-moving object that has a low speed; it covers a relatively small amount of distance in the same amount of time. An object with no movement at all has a zero speed. On the other hand, the velocity is just the speed with a direction meaning that it describes the rate at which an object changes its position. Imagine a person moving rapidly (fast speed) - one step forward and one step back - always returning to the original starting position. While this might result in a frenzy of activity, it would result in a zero velocity. Because the person always returns to the original position, the motion would never result in a change in position. Since velocity is defined as the rate at which the position changes, this motion results in zero velocity.