Which of the following correctly describes inertia?

Inertia is fundamentally defined as the property of matter that describes an object's resistance to changes in its state of motion. This means that an object at rest will remain at rest, and an object in motion will continue in motion at the same speed and in the same direction unless acted upon by a net external force. This concept is grounded in Newton's first law of motion, which states that an object will not change its motion unless a force acts on it.

When considering the other options, the second option refers to terminal velocity, which involves forces like drag and gravity acting on an object, but it does not pertain to the concept of inertia itself. The third option addresses kinetic energy, which relates to the energy of motion rather than the concept of resisting motion. The fourth option speaks about potential energy, which is about the energy stored due to an object's position in a gravitational field, again not connected to the resistance to change in motion.

The correct understanding of inertia is essential in mechanics, as it lays the foundation for analyzing motion and forces acting on an object.