‘反射’ (fǎn shè) literally combines ‘反’ (fǎn), meaning 'back' or 'reverse', and ‘射’ (shè), meaning 'to shoot' or 'to emit'. Together, they describe the physical phenomenon where light, sound, or other waves bounce back after hitting a surface — i.e., reflection. It is used primarily in scientific and technical contexts, especially in physics, biology (e.g., neural reflexes), and engineering.

In everyday language, ‘反射’ appears in both literal and figurative senses: it can refer to optical reflection (e.g., sunlight reflecting off water), acoustic reflection (echoes), or even automatic physiological responses like the knee-jerk reflex. Unlike the more general word ‘反映’ (fǎn yìng), which means 'to reflect' metaphorically (e.g., to represent or mirror reality), ‘反射’ is strictly tied to physical wave behavior or involuntary biological responses. It is commonly found in textbooks, medical reports, and science discussions.