Those who learn from the same teacher are called "friends", while those who share the same goals are called "friends", which is what the ancients said: "A fellow teacher is called a friend, and a comrade is called a friend." Zheng Xuan's Notes "Zhou Li·Di Guan· "Da Situ"). Mr. Wang Li's "Ancient Chinese" also uses this saying: "There is a difference between friends and friends in ancient times. Fellow disciples (teachers) are friends, and comrades are friends." That is to say, taking the word "friend" as an example, the ancients valued "different ways." "Consult with each other", hoping that like-minded people can discuss issues together, etc. There is a poem in "The Book of Songs·Xiaoya·Lumbering" that says "Listen to the sound of others, and ask for their friends' voices". The connotation is that people need to have the same interests and spirit. Like-minded people come to promote each other. There is a similar saying in "Book of Rites·Xue Ji": "Studying alone without friends will lead to loneliness and ignorance." Obviously, the "friends" here refer to "people of the same mind" and are not "friends". replaced. However, since "friends" with the same interests can easily fall in love with the same teacher and become "friends", "friends" of the same teacher may also be influenced by the teacher and develop similar interests and become "friends", so Later, it was difficult to distinguish between "friend" and "friend", and a stable structure like "friend" emerged.