Sometimes called the Lotus school (i.e. Hokkeshū, from the Jap. for Lotus Sūtra, Hokekyo), Tendai evolved as a distinctively Chinese interpretation of the enormous variety of Indian Buddhist sūtras available in Chinese translation by the 6th cent. Chih-i developed a comprehensive synthesis of this literature by arranging them chronologically into five periods of the Buddha's career, four methods of teaching, and four types of doctrine.
In 788 a Japanese Buddhist monk named Saichō (Dengyō Daishi, 766–822) established a small temple NW of Kyōto on Mount Hiei. Saichō studied Tendai in China during the year 804, and after his return to Japan introduced it in his temple, Enryaku-ji, on Mount Hiei. With the emperor's approval he ordained 100 disciples in 807. The traditional Tendai synthesis of Buddhist teaching and practice was maintained by Saichō, but he also widened this tradition by introducing a number of doctrines and practices of the esoteric tradition of Buddhism, known in Japanese as Shingon or ‘True Word’, which was being taught by his contemporary Kūkai on Mount Kōya. Later, especially under his successor Ennin, the esoteric tradition of Buddhism came to dominate Japanese Tendai even though Chinese Tʾien-tʾai maintained its distance from it. A further synthesis of Japanese Tendai occurred when attempts were made to include Shinto beliefs and practices under the name ichijitsu shintō (‘One-truth Shinto’).
The Tendai school is also of major historical importance since it was, because of its synthesis of the major forms of Buddhist teaching and practice, the source of the four 12th-cent. ‘Kamakura schools’ of Japanese Buddhism. Hōnen (1133–1212) the founder of Jōdo Shū (Pure Land school), Shinran (1173–1262) the founder of Jōdo Shinshū (True Pure Land school), Eisai (1141–1215) the founder of Japanese Rinzai Zen, Dōgen (1200–53) the founder of Japanese Sōtō Zen, and Nichiren (1222–82) the founder of the Nichiren school were all trained at Enryaku-ji. In the 10th cent., disputes between successors of Ennin and Enchin (814–91) led to two rival Tendai centres on Mount Hiei, with the Jimon-shū eventually setting up the Onjoji temple as its centre. A further schism in the 15th cent. was produced by Shinsei (1443–95), who introduced Pure Land elements and founded Tendai Shinsei-shū as a result. In recent years Tendai has looked for a revival through the Ichigū o terasu undō (‘Brighten a corner’) movement, which has sought to popularize Saichō's teaching, but Tendai remains small in comparison with other sects such as Nichiren or Zen.
"Tendai Shū." The Concise Oxford Dictionary of World Religions. . Encyclopedia.com. (April 18, 2019). https://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/tendai-shu
"Tendai Shū." The Concise Oxford Dictionary of World Religions. . Retrieved April 18, 2019 from Encyclopedia.com: https://www.encyclopedia.com/religion/dictionaries-thesauruses-pictures-and-press-releases/tendai-shu