law of reciprocity

例句：

1. 1. The law of reciprocity states that in a relationship, each party should give and receive equally.
   互惠法则指出，在关系中，每一方都应该给予和接受相等。
2. 2.In the field of economics, the law of reciprocity is often used to explain how trade benefits both parties.
   在经济学领域，互惠法则常用来解释贸易如何使双方受益。
3. 3. The principle of reciprocity is fundamental to any social contract, as it ensures that both parties are treated fairly.
   互惠原则是任何社会契约的基础，因为它确保了双方受到公平对待。