'开关' (kāi guān) literally combines '开' (to open) and '关' (to close), forming a compound that means 'switch' — a device used to turn electrical appliances on or off. As a noun, it most commonly refers to wall-mounted light switches, power buttons on electronics, or toggle controls in apps and interfaces. It’s a neutral, everyday term used across home, office, and digital contexts.

As a verb, '开关' functions as a separable verb: you say '把...开关' (bǎ... kāi guān) or use it with aspect particles like '了' — e.g., '开关了灯' is incorrect; instead, you say '把灯开关了' (colloquial but common) or more standardly '把灯打开了/关上了'. However, the verbal usage is far less frequent than the noun usage, and learners should prioritize mastering its noun sense first.