Which concept refers to the measure of resistance to a change in velocity?

Inertia is the concept that describes the measure of an object's resistance to a change in its state of motion, specifically its velocity. When an object is at rest, it tends to stay at rest, and when it is in motion, it tends to continue moving at a constant velocity unless acted upon by an external force. This principle is a part of Newton's First Law of Motion, which states that an object will remain at rest or in uniform motion in a straight line unless acted upon by a net external force.

While velocity, acceleration, and mass are fundamental concepts in physics, they do not directly refer to the resistance to changes in velocity. Velocity measures how fast an object is moving in a specific direction, acceleration refers to the rate of change of velocity, and mass is a measure of the amount of matter in an object, which is a contributing factor in determining inertia but not the direct measure of resistance itself.