A lunary, also called a selenodromion or moonbook, is a book of prognostication based on the position of the moon at any given time. It is an astrological genre with parallels as far back as Akkadian literature. From the 2nd century AD, it is common in the Greco-Roman world. There are examples in Greek, Latin, Coptic, Middle English and Old Nubian. Pagan, Jewish and Christian examples are known. The lunary was "by far the most popular and widely circulated prognostic genre" during the Middle Ages.
