altar, table or platform for the performance of religious sacrifice. In its simplest form the altar is a small pile, with a square or circular surface, made of stone or wood. Its features vary according to its purpose. The altar of libation usually has a drain for the liquid, and so does the altar of bloody sacrifice; the altar of burnt offering (including incense) often has a depressed hollow for a fire. Altars in Egypt, in Mesopotamia, in Greece, in Rome, and among the Aztec and the Maya were highly adorned with friezes, cornices, elaborate platforms, and canopies. At Pergamum there was a huge monumental altar 40 ft (12.2 m) high. Altars as a rule were out of doors in the ancient world and in Central America. The Christian altar is the place to celebrate the Eucharist, a sacrifice in the traditional view. In the Western Church the altar is a long, narrow table of stone or wood, often reminiscent of a tomb; at its back is a reredos, which often bears a canopy. In the Roman rite there are in the middle of the altar a crucifix and a tabernacle to contain the reserved Host, although recent legislation of Roman liturgical reform suggests that the tabernacle be placed elsewhere in the church. There is a recess in each altar containing bones of martyrs; this is even true of tiny portable altars carried by chaplains. In Eastern rites the altar is square and has no backing or reredos; it is away from the wall. Most Protestant denominations have no altar; a typical practice is to have a permanent communion table below and in front of the pulpit.

Raised structure or place used for sacrifice, worship, or prayer. Altars probably originated with the belief that objects or places (e.g., a tree or spring) were inhabited by spirits or deities worthy of prayers or gifts. Sacrifice to deities required a structure on which the victim could be killed and blood channeled off or flesh burned. In ancient Israel, the altar was a rectangular stone with a hollowed-out basin on top. The ancient Greeks placed altars (see baetylus) in homes, marketplaces, public buildings, and sacred groves. Roman altars were similarly ubiquitous and were often decorated with relief sculptures. Christians at first did not use altars, but by the 3rd century the table on which the Eucharist was celebrated was regarded as an altar. It became the focus of the mass in Christian churches and in Western churches was often adorned by a baldachin and an altarpiece.

Learn more about altar with a free trial on Britannica.com.