Speed is a variable that characterizes the movement of things and persons, representing the expediency with which to perform a movement or a movement through space, basically it's a physical quantity expressing the space covered by a mobile unit of time. It's dimensions are [length] / [time]. His unit in the International System is the m / s.
Speed is the physical quantity that expresses the sample and variation in position of an object and in function of time, which would be the same as saying that it's the distance traveled by an object in the unit time. But in addition to time, to define the speed of an object, it will be necessary to take into account the direction and meaning of that shift.
By its vector character, to set the speed should be considered the direction of travel and the module, which is called speed or quickness.
Speed is a concept widely used in the world of sports as well, since a large part of the sports played, such as football, basketball, hockey, tennis, among others, require significant preparation on this, and that the resistance is achieved at speed, much will depend on the success that the athlete gets in his career.