sidelight; side light; running light
Nautical term for the red (port) and green (starboard) navigation lights on a vessel.
Sidelights must be lit during nighttime navigation.
The port sidelight is red, and the starboard one is green.
Mixed kanji-kana spelling; less common but still encountered.
舷 (げん, 'gunwale, side of a ship') + 灯 (とう, 'light'). A straightforward compound describing the side-mounted navigation lights on a vessel.