What term is synonymous with photon?

The term that is synonymous with photon is quantum. In the context of physics, a photon is considered a quantum of electromagnetic radiation. It represents the smallest discrete amount of energy—specifically, the energy carried by a single particle of light.

While 'wave', 'particle', and 'energy' are also related to the concept of photons, they do not accurately reflect the term's definition. The dual nature of light encapsulates both wave and particle characteristics, but when specifically referring to a photon, 'quantum' is the term that directly relates to its fundamental nature as a unit of energy in quantum mechanics. Thus, identifying the photon as a 'quantum' emphasizes its role in the quantization of energy in electromagnetic fields.