A pyx, which can also be spelled “pix,” is a small box or container of sorts that is used in Roman Catholic and Anglican religious practice to carry the Eucharist to members of the church who are unable to travel to receive Holy Communion.
Most often, a church official uses a pyx to carry the Eucharist to the sick, injured, disabled, or invalid individuals of the religious community. It is also common for a missionary to carry a pyx so that he may transport the Eucharist on missions. With simply a pyx filled with the Eucharist and a breviary to guide the ceremony, a missionary might be able to offer communion to a large group.
Over the centuries the pyx has been recreated and redesigned. There are some that are made of metal, while others are made of glass or wood. They range from elaborate to plain, large to palm-sized. Almost every pyx, however, is round so as to fit or simply reflect the shape of the host inside. Every pyx is made with a fitted cover. Most of the modern ones are about the size and shape of a pocket watch and open like clamshells.
The term “pyx” comes from the Greek word pyxis, which means box or container. The plural form of the word is "pyxides." The term "burse" is used to describe a fabric bag or pouch that is used to transport a pyx. As the term has been used for many years and translated into use by different sects and churches, the word “pyx” does have varying meaning in some religious communities. In Roman Catholic practice, a pyx might also be referred to as a “lunette.” In Greek Catholic churches and Eastern Orthodox churches, the word pyx may be used to describe the tabernacle that is used to hold a host that is meant specifically for Lent.
Although the design, shape, components, and specific use of the pyx has changed over the years, it has always been a container meant to hold or transport that Eucharist. In this sense, the function of the pyx has never changed. An ornate silver pyx the size of a small melon used in 15th century Spain has exactly the same purpose of a small glass pyx used in the Bronx today.