The modern word "Senate" is derived from the Latin word "senātus" (senate), which comes from "senex", 'old man'. The members or legislators of a senate are called senators. The Latin word "senator" was adopted into English with no change in spelling. Its meaning is derived from a very ancient form of social organization, in which advisory or decision-making powers are reserved for the eldest men. For the same reason, the word "senate" is correctly used when referring to any powerful authority characteristically composed by the eldest members of a community, as a deliberative body of a faculty in an institution of higher learning is often called a senate. This form adaptation was used to show the power of those in body and for the decision-making process to be thorough, which could take a long period of time. The original senate was the Roman Senate, which lasted until at least AD 603, although various efforts to revive it were made in Medieval Rome. In the Eastern Roman Empire, the Byzantine Senate continued until the Fourth Crusade, circa 1202–1204.