In physics, the term for the resistance of an object to changes in its state of motion is called inertia. Inertia is a property of matter that dictates that objects at rest tend to remain at rest, while objects in motion continue in their motion unless acted upon by an external force. This concept is encapsulated in Newton's first law of motion, which states that the state of motion of an object will not change unless a net force is applied. Inertia plays a crucial role in understanding dynamics and the behavior of physical systems.