Rotational inertia, also known as moment of inertia, is a property of an object that quantifies how difficult it is to change its rotational motion. It depends on both the mass of the object and how that mass is distributed relative to the axis of rotation. The farther the mass is from the axis, the greater the rotational inertia. In practical terms, a spinning top with most of its weight near the tip will be easier to spin than a hula hoop with its mass distributed far from the center. Understanding rotational inertia is essential in fields like mechanical engineering and physics, where it influences the design and stability of rotating systems.