A conservative system is a physical system in which the total mechanical energy remains constant over time. This means that the sum of kinetic energy and potential energy does not change, as long as no external forces do work on the system. Examples of conservative forces include gravity and spring forces, which can store energy without dissipating it. In conservative systems, energy can be transformed from one form to another, but the total energy is conserved. This principle is fundamental in physics and helps in analyzing various phenomena, such as the motion of planets in space or the oscillation of a pendulum.