What is "lychnapsia"

In the Roman Empire, the Lychnapsia was a festival of lamps on August 12, widely regarded by scholars as having been held in honor of Isis. It was thus one of several official Roman holidays and observances that publicly linked the cult of Isis with Imperial cult. It is thought to be a Roman adaptation of Egyptian religious ceremonies celebrating the birthday of Isis. By the 4th century, Isiac cult was thoroughly integrated into traditional Roman religious practice, but evidence that Isis was honored by the Lychnapsia is indirect, and lychnapsia is a general word in Greek for festive lamp-lighting. In the 5th century, lychnapsia could be synonymous with lychnikon (lamp-lighting at vespers) as a Christian liturgical office.