Pyx
A pyx or pix is a small round container used in the Catholic, Old Catholic, Lutheran and Anglican Churches to carry the Eucharist, to the sick or those who are otherwise unable to come to a church in order to receive Holy Communion. The term can also be used in archaeology and art history to describe small, round lidded boxes designed for any purpose from antiquity or the Middle Ages, such as those used to hold coins for the Trial of the Pyx in England.
Usage
The word pyx comes from the Greek word πυξίς, pyxis 'box, receptacle'. While the word may be applied to any covered carrier, in modern usage the term "pyx" usually denotes a small, flat, clamshell-style container, often about the size of a pocket watch and usually made of brass or other metals,traditionally lined with gold.
A fabric or leather pouch for carrying a pyx is known as a burse. Typically, this kind of burse can be securely closed and is fixed with cords so that the priest, deacon, or extraordinary minister of Holy Communion can affix it to his or her person during transport to prevent the consecrated host from being accidentally lost.
These objects, and others, such as the lunette that contain a consecrated host, are normally kept within the church tabernacle when they are not being carried. The tabernacle may be behind the main altar, at a side altar, or within a special Eucharistic chapel.