"Xin" refers to keeping one's word and being faithful. It is one of the "Five Constant Virtues" (namely, benevolence, righteousness, courtesy, wisdom and faithfulness) of Confucianism. Faithfulness, put forward by Confucius and his disciples, requires people to keep their words according to the rules of courtesy with the hope of mitigating the conflicts in the ruling class and between the opposing classes.

Confucius held "faithfulness" to be an indispensable virtue for a human being. Only a man of faithfulness would be appointed to some task; otherwise survival would be hardly possible. Confucius called the man without faith mean person and kept an aloof distance with them.

Faithfulness is regarded by Confucianism as the basis for building and administrating a country. The rulers and the state administrators should, first of all, win the faith of the people before calling upon them; otherwise it would be misunderstood as the torture for them. Only when the ruler keeps his word, would the governed people be willing to be honest and faithful.

For Confucianism, faithfulness is of great significance in interpersonal communication and state administration.