Emperor in Chinese is 帝 (di4) or 皇帝(hua2ngdi4). The Chinese were much more pragmatic about their emperors than the Japanese. They believed that they had some divine blood in them, but that they could just as easily fall from divine grace as anyone else (losing Heaven's Mandate). The Japanese, however, were (and are) very adamant that their emperor is a direct descendant of the Divine. 天子 is only used in Japan.