The word "熄灯" is formed by combining the character "熄", meaning to extinguish, which is composed of the fire radical (火) indicating relation to fire and the phonetic component "息" providing sound and semantic reinforcement, with the character "灯", meaning lamp or light, composed of the fire radical (火) indicating relation to light and the phonetic component "丁" providing sound; together, "熄" denotes the action of putting out, and "灯" specifies the object, resulting in the meaning "turn off the lights".