Ap'otheo'sis (deification), a solemnity among the ancients by which a mortal was raised to the rank of the gods. The custom of placing among the gods those mortals who had rendered their countrymen important services was very ancient among the Greeks. The Romans, for several centuries, deified none but Romulus, and first imitated the Greeks in the fashion of frequent apotheosis after the time of Caesar. From this period apotheosis was regulated by the decrees of the senate and accompanied with great solemnities. Many of the Roman emperors were deified.