The principle that states energy cannot be created or destroyed is known as the law of conservation of energy. This fundamental concept in physics asserts that the total amount of energy in a closed system remains constant over time. While energy can change forms—from kinetic to potential, for instance, or from thermal to mechanical—it cannot be created from nothing or eliminated entirely. This law is crucial for understanding various physical processes, including mechanical work, thermodynamics, and the behavior of systems. The conservation of energy principle lays the foundation for many scientific theories and practical applications.