The Proper (Latin proprium) is a part of the Christian liturgy that varies according to the date, either representing an observance within the Liturgical Year, or of a particular saint or significant event. The term is used in contrast to the ordinary, which is that part of the liturgy that is reasonably constant, or at least selected without regard to date, or to the common, which contains those parts of the liturgy that are common to an entire category of saints, such as Apostles or Martyrs. Propers may include hymns and prayers in the Canonical Hours and in the Eucharist.