Ostensorium

A monstrance, also known as an ostensorium (or an ostensory), is the vessel used in Roman Catholic, Old Catholic and Anglican churches for the more convenient exhibition of some object of piety, such as the consecrated Eucharistic host during Eucharistic adoration or Benediction of the Blessed Sacrament. It is also used as reliquary for the public display of relics of some saints. The word monstrance comes from the Latin word monstrare, while the word ostensorium came from the Latin word ostendere. Both terms, meaning "to show", are used for vessels intended for the exposition of the Blessed Sacrament, but ostensorium has only this meaning.

In the Catholic tradition, at the moment of consecration the elements (called "gifts" for liturgical purposes) are transformed (literally transubstantiated) into the body and blood of Christ. Catholic doctrine holds that the elements are not only spiritually transformed, but are (substantially) transformed into the body and blood of Christ. Although the elements retain the appearance, or "accidents," of bread and wine, they become the body and blood of Christ. The presence of Jesus in the Eucharist is known as the doctrine of the Real Presence within the Roman Catholic tradition. Other Christians (notably Anglicans, Old Catholics, Mar Thoma, and Lutherans) accept the doctrine of the Real Presence, whilst rejecting transubstantiation as a philosophical concept. Owing to these beliefs, the consecrated elements are given the same adoration and devotion that Christians of these traditions accord to Christ himself.

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