noun
under the lamp; by the lamp
Literary or somewhat old-fashioned word for the area illuminated by a lamp or lantern. Often used in poetic or descriptive contexts.
灯下に本を広げて読む。
I spread out a book and read under the lamp.
灯下の影が壁に揺れていた。
The shadow under the lamp flickered on the wall.
灯火 means 'lamp light' or 'lamplight' itself, while 灯下 refers to the area or space under the lamp.
Compound of 灯 (tō, 'lamp') and 下 (ka, 'under'). The reading is on'yomi. The word is straightforward in formation, but its usage is largely literary.