Momentum is a physical quantity that describes the motion of an object and is defined as the product of its mass and velocity. Mathematically, it is expressed as ( p = mv ), where ( p ) represents momentum, ( m ) is mass, and ( v ) is velocity. Momentum is a vector quantity, meaning it has both magnitude and direction. It is conserved in isolated systems, which means the total momentum before an event (like a collision) is equal to the total momentum after the event.