Angular momentum is a fundamental physical quantity that characterizes the rotational motion of an object or system. It is the rotational analog of linear momentum, describing the quantity of rotation associated with a mass distributed about an axis. Mathematically, it is proportional to both the moment of inertia of the system and its angular velocity. The principle of conservation of angular momentum states that if no external torque acts upon a rotating system, the total angular momentum of that system will remain constant, regardless of changes in the distribution of mass or changes in rotational speed. This conservation law is a foundational principle in celestial mechanics and the study of rigid body dynamics, explaining phenomena from planetary orbits to the spinning motion of macroscopic objects.