In ancient China, foreign countries were called Fan. Out of respect, submission and other reasons, these countries will send envoys to see the emperor. Many foreign envoys gathered in the court, and in order to facilitate the emperor's understanding one by one, the minister in charge of the ceremony divided the envoys into two rows. According to the order, the emperor first talked with the envoys from left to right, and so on. Before the conversation, the ceremonial officers will report the titles of these foreign countries, that is, the so-called serial numbers
the serial numbers have the meaning of numbering in turn. In modern Chinese, the serial number generally refers to the army number, which is mainly awarded according to the nature, establishment sequence and numerical order of the army.
The origin and meaning of the word serial number