釋氏要覽 3.390

3.390

釋氏死。謂涅槃。圓寂。歸真。歸寂。滅度。遷化。順世。皆一義也。隨便稱之。蓋異俗也。

The death of a Buddhist is called nirvāṇa, complete stillness, returning to truth, returning to stillness, extinction-deliverance, transformation-transition, or submitting to the worldly course. These are all one meaning. They are termed according to convenience, broadly to distinguish them from secular practice.