Relative motion is the study of the motion of one object with respect to another object. This branch of physics and mechanics focuses on how the motion of one object is perceived or measured by an observer in reference to a different object. It involves analyzing the speed, direction, and acceleration of objects moving in relation to each other, taking into account factors such as frames of reference, velocity, and position. Relative motion is commonly applied in fields such as astrophysics, engineering, and kinematics to understand the movement and interactions of objects in various systems.