礼尚往来 (lǐ shàng wǎng lái) - Reciprocity

礼尚往来 is an idiom meaning "courtesy demands reciprocity," reflecting the cultural importance of mutual respect and exchange.

Example: 他送我礼物，我也要回礼，礼尚往来 (Tā sòng wǒ lǐwù, wǒ yě yào huílǐ, lǐ shàng wǎng lái) - He gave me a gift, so I must reciprocate; courtesy demands reciprocity.

Fact: This principle is deeply rooted in Chinese customs and is often seen in gift-giving practices, where the value of gifts exchanged should be roughly equivalent.

Source: Mandarin Inn