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An academy is an institution of secondary education, higher learning, research, or honorary membership. Academia is the worldwide group composed of professors and researchers at institutes of higher learning.

The emperor Justinian closed the school in AD 529, a date that is often cited as the end of Antiquity. According to the sole witness, the historian Agathias, its remaining members looked for protection under the rule of Sassanid king Khosrau I in his capital at Ctesiphon, carrying with them precious scrolls of literature and philosophy, and to a lesser degree of science. After a peace treaty between the Persian and the Byzantine empire in 532 guaranteed their personal security (an early document in the history of freedom of religion), some members found sanctuary in the pagan stronghold of Harran, near Edessa. One of the last leading figures of this group was Simplicius, a pupil of Damascius, the last head of the Athenian school.

Under the Sasanians, Syriac became an important language of the administration and intellectuals, rivaling Greek. Several cities developed centers of higher learning in the Sasanian Empire, including Mosul, al-Hira, and Harran (famous for the Pythagorean School of the Sabeans). The Grand School was the main center of learning in the Persian capital Ctesiphon, but little is known about it. Perhaps the most famous center of learning in Persia was the Academy of Gundishapur, teaching medicine, mathematics, astronomy, and logic. The academy was later instrumental in founding the Muslim city of Baghdad as a center of learning, and serving as the model for the first Muslim hospital (bimaristan) at Damascus.

In Florence, the Medici again took the lead in establishing the Accademia e Compagnia delle Arti del Disegno in 1563, the first of the more formally organised art academies that gradually displaced the medieval artists' guilds, usually known as the Guild of Saint Luke, as the bodies responsible for training and often regulating artists, a change with great implications for the development of art, leading to the styles known as Academic art. The private Accademia degli Incamminati set up later in the century in Bologna by the Carracci brothers was also extremely influential, and with the Accademia di San Luca of Rome (founded 1593) helped to confirm the use of the term for these institutions.

The Accademia degli Infiammati of Padova and the Accademia degli Umidi, soon renamed the Accademia Fiorentina, of Florence were both founded in 1540, and were both initially concerned with the proper basis for literary use of the volgare, or vernacular language of Italy, which would later become the Italian language. In 1582 five Florentine literati gathered and founded the Accademia della Crusca to demonstrate and conserve the beauty of the Florentine vernacular tongue, modelled upon the authors of the Trecento. The main instrument to do so was the Vocabolario degli Accademici della Crusca. The Crusca long remained a private institution, criticizing and opposing the official Accademia Fiorentina.

Academic societies or learned societies began as groups of academics who worked together or presented their work to each other. These informal groups later became organized and in many cases state-approved. Membership was restricted, usually requiring approval of the current members and often total membership was limited to a specific number. The Royal Society founded in 1660 was the first such academy. The American Academy of Arts and Sciences was begun in 1780 by many of the same people prominent in the American Revolution. Academic societies served both as a forum to present and publish academic work, the role now served by academic publishing, and as a means to sponsor research and support academics, a role they still serve. Membership in academic societies is still a matter of prestige in modern academia.

The Academy of Motion Picture Arts and Sciences, which presents the annual Academy Awards, is an example of a purely industry body using the name. College-type specialized academies include the Royal Academy of Music of the United Kingdom; the United States Military Academy at West Point, New York; the United States Naval Academy; United States Air Force Academy; and the Australian Defence Force Academy. In emulation of the military academies, police in the United States are trained in police academies.

Academia began to splinter from its Christian roots in 18th-century colonial America. In 1753, Benjamin Franklin established the Academy and Charitable School of the Province of Pennsylvania. In 1755, it was renamed the College and Academy and Charitable School of Philadelphia. Today, it is known as the University of Pennsylvania. For the first time, academia was established as a secular institution. For the most part, church-based dogmatic points of view were no longer thrust upon students in the examination of their subjects of study. Points of view became more varied as students were free to wander in thought without having to add religious dimensions to their conclusions.