Final answer:
The baptism is administered in a baptistery, which is either a part of the church or a separate building associated with it.
Step-by-step explanation:
The part of a church or a separate building in which baptism is administered is called a baptistery. A baptistery is a designated area within a church or a separate building associated with the church that contains a baptismal font for performing the sacrament of Christian baptism. During the Renaissance, it was common for baptisteries to be separate buildings, particularly in places like Florence, which was a center for Renaissance art and architecture. This separation allowed people to be baptized before entering the main part of the church. In contrast, the nave is the central aisle of the church, the chancel is the area where the clergy lead the ceremonies, and the altar is where the Eucharist is celebrated.