Distance - Time Graph

The slope of distance time graph is said to be speed.

The distance - time graph is a straight line for such body whose motion is uniform.

The distance - time graph is not a straight line for such body whose motion is non - uniform.

The slope of displacement - time graph is said to be velocity.

The slope of displacement - time graph is said to be velocity.

The velocity time graph is said to be Acceleration.

The area described by velocity - time graph is said to be distance.

The rate of change of velocity per unit time of a moving body is said to be acceleration.It is generally denoted by "a".
Therefore,
a = (v - u)/t

Speed and Velocity

Speed
The rate of change of distance per unit time of a moving body is called speed.Speed = distance/time The SI unit of speed is metre per second. Speed is a scalar quantity.
Average speed
Total distance which is covered by a body is divided by total time taken of moving body is said to be average speed.Average speed = Total distance/Total time taken.
Velocity
The rate of change of displacement per unit time of a moving body is said to be velocity.Velocity = Displacement/Time The SI unit of velocity is metre per second. Velocity is a vector quantity.
Average Velocity
Average of initial and final velocity of a moving body is said to be average velocity.Average velocity = (Initial velocity + Final Velocity)/2.