I don't know if you have found that from the beginning of the Han Dynasty, we used to call a certain emperor emperor, such as Emperor Wu of Han, Emperor Ling of Han, Emperor Xian of Han, etc., but later in the Tang and Song Dynasties we called emperors all so-and-so, such as Tang Taizong, Tang Xuanzong, Song Huizong, Song Qinzong, so why is this? Why are the same emperors, their titles different?
Since the Han Dynasty, people have used to use the title of emperor, which is a title that is based on his life deeds and moral cultivation after death, based on good intentions or a title with critical evaluation. The origin of the title system is unknown, but it can be traced back to around the time of King Mu of Zhou, until Qin Shi Huang abolished the title after he unified China. The emperor was called several lifetimes, such as the Qin II we called, but the Qin Dynasty only experienced two lifetimes, and was replaced by the Han Dynasty founded by Liu Bang, who restored the system of titles to continue. Therefore, the emperor of the Han Dynasty had a nickname again, and still followed the previous rules, objectively and fairly evaluated the emperor, and the emperor who did not do well would install a bad title to show criticism, and the "spirit" in the Han Ling Emperor was actually a pejorative meaning.
However, after the Wei and Jin Dynasties, the title began to change its flavor, becoming a weapon of flattery, usually only praising and not depreciating, and the number of words in the name also increased, from the initial one or two words to seven or eight words, and by the time of the Ming Dynasty, it was already more than a dozen words. For example, Zhu Di, the third emperor of the Ming Dynasty, was called Emperor Taizong Tianhong Dao Gao Ming Guangyun Holy Relic God Gong Zhi Xiaoren Emperor, and it was a bit too complicated to use the title to refer to the emperor at this time. You can't use a nickname, so what to do?
Only temple numbers can be used. Temple number is a praise of the character, originated from the Shang Dynasty that attached importance to sacrifice and worship, before the Wei and Jin Southern and Northern Dynasties, the temple number was very strictly controlled, only the first emperor who had meritorious service to the country and was worthy of eternal sacrifice for future generations could add the temple number, but after the Wei and Jin Dynasties, as the number changed, the temple number also changed its flavor. Any emperor can have a temple number, because the temple number only needs one word to express its meaning, and there is no distinction between praise and criticism, and after the abuse of the temple number, historians began to use the temple number to refer to the emperor.
From the beginning of the Tang Dynasty, the emperor was called by temple numbers, Tang Taizong, Tang Gaozong, Song Taizu, Song Shenzong, these titles are from the temple number, whether it is the emperor or the emperor, it must be the title of the later people, when the emperor was alive, absolutely no one called it so, you should understand it here.
So when we are reading a book, or when watching a TV series, you must know what it is and why it is so that you can have your own talking points when chatting with everyone after tea.