noun
nightlight; all-night lamp
A light kept burning throughout the night, often for safety, religious, or decorative purposes. Can refer to small modern nightlights or traditional lamps.
廊下に常夜灯をつけておく。
I leave a nightlight on in the hallway.
神社の常夜灯が夜道を照らしていた。
The shrine's all-night lamp lit the path at night.