* Acceleration is the rate of change of velocity. Velocity has both speed and direction.

* Gravity constantly pulls objects towards the center of the Earth. This pull changes the velocity of objects in two ways:

* Speed: Objects falling under gravity get faster as they descend.

* Direction: Gravity constantly changes the direction of an object's motion, even if it's initially moving horizontally. Think of a ball thrown across a field – it curves downwards due to gravity.

Therefore, since gravity causes a change in velocity, it's considered an acceleration.

Important Note: The acceleration due to gravity is constant near the surface of the Earth and is approximately 9.8 m/s². This means that for every second an object falls, its velocity increases by 9.8 meters per second.