If something moves from position to position then speed is a measure of how fast it moved. Speed is defined as the distance moved divided by the time needed to move. Both change in position or distance and time are measured quantities. Frequently speed is called the time rate of change of distance. For example, if you drive 240 miles in 4 hours then your speed is 60 miles per hour (abbreviated mph). It is unlikely that you drove the whole trip at a constant 60 mph; this example calculated your average speed. If you were pulled over for speeding and were told you were going 80 mph, you wouldn’t be able to avoid a ticket by saying “But officer, my average speed is only 60!”