Tian (天) is one of the oldest Chinese terms for heaven and a key concept in Chinese mythology, philosophy, and religion. During the Shang dynasty (17th―11th century BCE), the Chinese referred to their highest god as Shangdi or Di (帝, 'Lord'). During the following Zhou dynasty, Tian became synonymous with this figure. Before the 20th century, worship of Tian was an orthodox state religion of China. In Taoism and Confucianism, Tian (the celestial aspect of the cosmos, often translated as "Heaven") is mentioned in relationship to its complementary aspect of Dì (地, often translated as "Earth").
https://en.wikipedia.org/wiki/Tian