What is the definition of speed?

Answer 1

Speed is distance traveled through motion per some unit of time. It can also be defined as the rate of change in position along a single path. Speed is a scalar value, not a directional one.

It is similar to the definition of "velocity", except that in "velocity", the direction is also important. If the velocity is constant, you can simply divide distance traveled by time. The general case, however, is that velocity is the derivative of position, with respect to time. In symbols: v = ds/dt. If you are not familiar with derivatives, this basically means that to get the instant velocity, you divide the distance traveled by the time it takes, for a very short time period.
Speed is the Distance covered per unit time. where as velocity is the Displacement per unit time. Distance is the actual length covered by the Object between two endpoints & Displacement is the length in the straight line between two points.