Reciprocity is a social principle where individuals respond to positive actions with similar positive actions. This concept is often seen in relationships, where one person's kindness or help encourages the other to return the favor. It fosters cooperation and builds trust among people, making it a fundamental aspect of social interactions. In psychology and sociology, reciprocity can influence behavior and decision-making. For example, in marketing, businesses often use reciprocity by offering free samples or gifts, hoping customers will feel compelled to make a purchase in return. This principle is also evident in various cultures and communities, where mutual support strengthens social bonds.