Proper (liturgy)
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.
West
In Roman Catholic and Anglo-Catholic practice, there is a moveable portion of the service that, strictly speaking, does not form part of the proper, the Accentus. The Proper of the Mass, strictly speaking, consists of the Introit, Gradual, Alleluia or Tract, Sequence, Offertory, and Communion. Portions of the Accentus may also more loosely be referred to as part of the "Proper" if they satisfy the criteria of changing by date (such as the Preface and Epistle).
East
In the Eastern Orthodox and Greek-Catholic Churches, the propers at Vespers and Matins are numerous. At the Little Hours they will normally include only the Troparion and Kontakion.
At the Divine Liturgy they may include the Troparion, Kontakion, Prokeimenon, the readings from the Apostle and Gospel, the Zadostoinik (hymn replacing It is Truly Meet and the Communion Hymn. On Great Feasts of the Lord ther will also be special Antiphons that replace the psalms and beatitudes that normally begin the Liturgy.