There are these related phrases: - 켜다(turn on), 켜지다(come on), 켜져 있다(is on - a state). - 끄다(turn off), 꺼지다(go out), 꺼져 있다(is off). *켜지다/꺼지다 are passive forms of 켜다/끄다(transitive verbs). Examples: - I turned on the light: 나는 불을 켰다. ("불" means "light", or "fire"). - I turned off the light: 나는 불을 껐다. - The light came on: 불이 켜졌다. (or 불이 들어왔다). - The light went out: 불이 꺼졌다. (or 불이 나갔다). - The light [TV] is on: 불이 [티브이가] 켜져 있다. - The light [TV] is off: 불이 [티브이가] 꺼져 있다. In a noun modifying phrase, 켜져 있는/꺼져 있는 is very often simplified to 켜진/꺼진. - 불(이) 켜진 사무실들: Offices with lights on. - 불(이) 꺼진 창: A lightless window. (불이 꺼져 있는 창 is used when more clarity/emphasis is needed). - 꺼진 불도 다시 보자: Look again even when the fire appears out. (from a fire hazard awareness campaign)

The light is ON. 불(or 전기) 들어 왔어. 켜져 있어. 켜졌어. 켰어. The TV is OFF. 티브이 꺼져 있어. 꺼졌어. 껐어.