Tented roofs, a feature of medieval ecclesiastical architecture, were commonly employed to cover high, conical roof structures on churches. It had the shape of a polygonal spire but had a different purpose in that it was usually employed to roof the main internal area of a church rather than as an ancillary building. The word "tent" here means a large circular or polygonal room with a domed ceiling. These rooms were used for various purposes by medieval churches including as baptisteries, tombs, and refectories. The word "church" here refers to the main body or place of worship of a Christian congregation; it may be defined as "the place where Christians meet to hear God's Word preached and to celebrate the sacraments." In ancient times there was no distinction made between church and chapel, but nowadays the term "chapel" is generally applied to smaller buildings set aside for religious purposes while the term "church" denotes a larger institution with other functions attached to it. However, in early Christianity chapels were often built into the walls of homes where prayers could be said directly facing heaven; these became known as "tombs" because the occupants were saying farewell to life itself. Thus, a tent roof chapel is a small structure set next to a tomb which served as a place of prayer for those who lived there. In order to preserve heat during cold seasons and protect worshipers from rain, some medieval churches had tent-shaped roofs.