灯 is one of the most commonly used Japanese kanji, and it also has a lot of special readings in addition to the standard onyomi and kunyomi readings.
ONYOMI 音読み
ひ hi ほ- ho- ともしび tomoshibi とも.す tomo.su あかり akari
KUNYOMI 訓読み
トウ tou
Examples
窓に灯がともっていた。There was a light burning in the window.がは灯に集まる。Moths are attracted by light.パリは灯の都と呼ばれています。多くの美しい建物が夜になると点灯されます。Paris is called the City of Lights. Many beautiful buildings are lit at night.