In church architecture, the chancel is the space around the altar, including the choir and the sanctuary (sometimes called the presbytery), at the liturgical east end of a traditional Christian church building. It may terminate in an apse. It is generally the area used by the clergy and choir during worship, while the congregation is in the nave. This is one definition, sometimes called the "strict" one; in practice in churches where the eastern end contains other elements such as an ambulatory and side chapels, these are also often counted as part of the chancel, especially when discussing architecture. In smaller churches, where the altar is backed by the outside east wall, and there is no distinct choir, the chancel and sanctuary may be the same area. In churches with a retroquire area behind the altar, this may only be included in the broader definition of chancel.