What is the definition of energy?

The definition of energy as the ability to do work encapsulates the fundamental concept in physics that energy is a measure of the capacity to perform tasks or exert force over a distance. In various contexts, energy manifests in different forms, such as kinetic energy, potential energy, thermal energy, and chemical energy, but they all relate back to the overarching idea that energy enables changes or movements within a system.

This understanding aligns with various principles in physics that underline how energy is utilized in physical activity and exercise, where it is the driving force behind muscle contractions and movements. Essentially, when energy is expended, it translates to work being done, which can be observed in everyday actions like running, lifting weights, or even maintaining posture.

The other definitions provided do not encapsulate the broad nature of what energy is. For instance, defining energy as the capacity to change physical matter is limiting, as it does not account for work done without a change in matter. Similarly, stating that energy is the measure of physical motion mischaracterizes energy, which is not merely a measure but rather a capability that causes motion. Lastly, identifying energy solely as the force applied over a distance conflates two separate concepts—force and work—without giving a comprehensive view of energy itself.