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Speed is a scalar quantity, meaning it is a simple amount of something; it just includes how fast something is moving. In scientific terms, speed is often measured in meters per second, although both the units and the time vary in other applications; a car that's traveling at 60 miles per hour (mph) or 96.5 kilometers per hour (kph), for example, is moving at a specific speed. Only the rate of movement is required - how far the object is moving over a certain amount of time. This is the formula for speed:

Speed = Distance / Time

Velocity is a vector quantity, so it includes not only the amount, but also how it moves in space - the direction. Direction is determined by displacement, which is the distance between where the object started and where it stopped. This is not necessarily equal to the distance traveled; if point A and point B are 2 km apart, but a person walks a 3.5 km path to get from A to B, the displacement is still 2 km. The direction from point A to B must be included when describing this measurement, such as "1.4 meters per second, north."

This is the formula for velocity:

Velocity = Displacement / Time

Because velocity doesn't take the distance traveled into account, an object's average speed and its average velocity can be very different. If a person walks a 3.5 km path from point A to point B in 45 minutes, she has an average speed of 4.66 kph. If the displacement between A and B is only 2 km to the north, however, her average velocity is 2.66 kph, north.