What is the term for an elemental unit of energy?

The term for an elemental unit of energy is "quantum." In the context of physics, a quantum refers to the smallest discrete amount or package of energy that can exist in a system. This concept is fundamental in quantum mechanics, where energy is not continuous but is instead quantized, meaning it can only exist in specific amounts.

For example, when dealing with light, the quantum of energy corresponds to a photon, which can be thought of as a particle of light carrying a specific amount of energy determined by its frequency. However, while a photon represents a specific particle and its associated energy, the term “quantum” encapsulates the broader concept of discrete energy levels that can apply to various forms of energy, including sound, heat, and electromagnetic energy.

Other terms like volt and joule refer to units of measurement used in the context of electric potential and work or energy, respectively, but do not capture the idea of energy as being quantized at the elemental level. Thus, quantum is the most accurate term to use in this context.