The word 辐射 is formed through a vivid conceptual metaphor. It combines the character 辐 (fú), which originally refers to the spokes of a wheel radiating out from a central hub, with 射 (shè), meaning to shoot out or emit. Together, they create a compound that visually and conceptually captures the idea of something propagating or emitting energy outward in all directions from a single source, much like spokes from an axle or rays from the sun, ultimately representing the abstract concept of "radiation".