The apse of a church, cathedral, or basilica is often the semicircular or polygonal termination of the choir or sanctuary, or the end of an aisle. It is the name given to the space in church building where the altar is situated or where the clergy are sitting. The word comes from the Greek ἀφελής (aphēlḗs), meaning "without fault". This term was originally applied only to that part of the temple area which was reserved for the priests. But it came to include all that was sacred and holy, and today it is used for that portion of any structure devoted to religious purposes.
The apse can be divided into three parts: the wall of the apse, the vestibule of the apse, and the roof of the apse. The wall of the apse is that part of the structure which surrounds the entire apse. It may be made of stone or brick, but it usually has a door called an oculus, which provides access to the interior of the apse. The oculus may be covered by a window or stained glass panel. Sometimes the oculus is located at the side of the apse instead of the front. There may be other doors located on the wall of the apse to lead to other parts of the church. All these doors should be made of wood or metal and have locks.
An apse is a semicircular or polygonal end to a secular or religious building's choir, chancel, or aisle. The apse was first employed in pre-Christian Roman architecture as an expanded niche to accommodate a deity's statue in a temple. It is also found in Christian churches where one apse serves for both altar and choir.
The word "apse" comes from the Latin word meaning "to sit". In Christian churches with a nave and aisles, the priest stands during Holy Communion and other important ceremonies while people are seated elsewhere in the church. This idea came from the practice in early Christianity of everyone sitting in full view of the altar while only the priest had access to it. As churches became larger and priests could not walk throughout them, the idea of an apse arose so that both the altar and the people would have a place of honor.
In a Catholic church, the apse is where the altar and bishop's chair are located. It is a semi-circular recess on the wall of the church just above the level of the main floor containing facilities such as heating and air conditioning units. The term "Apse Bishop" is used when referring to the bishop who leads a particular diocese. The title "Apostle" is often used interchangeably with the title "Bishop", but this should be taken with a grain of salt because there are many more bishops than apostles.
The chancel is the space around the altar at the liturgical east end of a classic Christian church structure, containing the choir and the sanctuary (sometimes known as the presbytery). It might end in an apse. The word comes from the Latin caelum, meaning sky or heaven.
Early Christians did not have a specific name for this part of the church building. When they needed to refer to it they used general terms such as "the holy place" or "the place where the Lord will be worshiped." Its primary function was as a place of prayer where believers could come together to praise God and seek his guidance.
As Christianity grew and more elaborate churches were built, the chancel became a special place where priests could conduct important ceremonies. Gradually it came to be regarded as the most sacred part of the church, where saints and angels would meet with Jesus Christ on the right hand side near the altar. This area is now usually called the Holy Place or the Priest's Area.
In medieval churches the chancel was where the king or queen was crowned. A new chancel was built when royal authority changed hands or when old buildings were converted for other uses. The word "cancel" comes from this original use of the chancel.