Tian is one of the oldest Chinese terms for heaven and a key concept in Chinese mythology, philosophy, and religion. During the Shang Dynasty (17–11th centuries BCE), the Chinese referred to their supreme god as Shàngdì (, "Lord on High") or Dì (,"Lord"). During the following Zhou Dynasty, Tian became synonymous with this figure. Heaven worship was, before the 20th century, an orthodox state religion of China.