​CONSUETUDINARY (Med. Lat. consuetudinarius, from consuetudo, custom), customary, a term used especially of law based on custom as opposed to statutory or written law. As a noun “consuetudinary” (Lat. consuetudinarius, sc. liber) is the name given to a ritual book containing the forms and ceremonies used in the services of a particular monastery, cathedral or religious order.