Inertia is the tendency of an object to resist any change in its motion. This means that an object at rest will stay at rest, and an object in motion will stay in motion at a constant velocity, unless acted upon by an external force.

Examples of inertia include:

* A ball rolling down a hill will continue to roll down the hill until it encounters an obstacle, such as a tree or a wall.

* A car driving down the road will continue to drive down the road at the same speed until the driver brakes or turns the wheel.

* A person sitting in a chair will continue to sit in the chair until they stand up or are pushed out of the chair.

Inertia is a fundamental property of matter. It is what gives objects mass, and it is what makes it possible for objects to move. Without inertia, objects would not be able to resist changes in their motion, and the world would be a very chaotic place.