To turn off the light(s); to switch off illumination or electric lights. Common everyday expression. Also written 灯りを消す.
寝る前に必ず明かりを消す。
I always turn off the light before going to bed.
部屋を出るときは明かりを消してください。
Please turn off the lights when you leave the room.
節電のためにオフィスの明かりを消す時間を決めた。
To save electricity, we set a time to turn off the office lights.