An object is said to be in motion if its position changes with time relative to a chosen frame of reference. In simpler terms, when the location or position of an object changes with respect to its surroundings or a fixed point over time, it is considered to be in motion. Motion is a fundamental concept in physics and can be described in terms of displacement (change in position), distance (path length), velocity (rate of change of displacement), and acceleration (rate of change of velocity).