Speed:

The distance covered by an object in unit time is called speed.

$Speed = \frac{Distance \: covered}{Time \: taken}$

$v = \frac{S}{t}$

Velocity:

The rate of displacement of a body is called velocity.

$Velocity=\frac{Displacement}{Time \: taken}$

$v = \frac{D}{t}$

Acceleration:

Acceleration is defined as the rate of change of velocity of a body

$acceleration = \frac{Change \: of \: velocity}{Time \: taken}$

$acceleration = \frac{final \: velocity \: - \: initial \: velocity}{Time \: taken}$

$a=\frac{vf \: - \: vi}{t}$

Unit of acceleration:

SI unit of acceleration is a meter per second square.