The ordinary, in Roman Catholic and other Western Christian liturgies, refers to the part of the Eucharist or of the canonical hours that is reasonably constant without regard to the date on which the service is performed. It is contrasted to the "proper", which is that part of these liturgies that varies according to the date, either representing an observance within the liturgical year, or of a particular saint or significant event, or to the "common" which contains those parts that are common to an entire category of saints such as apostles or martyrs.