Yuan Zhen and Bai Juyi are known together as the "Great Poet Pair" or "Tang Dynasty Poet Pair." This moniker reflects their significant contributions to Chinese literature during the Tang Dynasty. Both poets are celebrated for their elegant and profound works, which have had a lasting impact on Chinese poetry and culture.

The term "Great Poet Pair" is fitting because Yuan Zhen and Bai Juyi were contemporaries and shared a deep mutual respect for each other's work. They were both part of the "Eight Great Poets" of the Tang Dynasty, a group of poets who were renowned for their lyrical talents and poetic innovation. Their collaboration and influence on each other's poetry are evident in their shared themes, styles, and the evolution of their poetic techniques.

Yuan Zhen (772-831) and Bai Juyi (772-846) were both born in the same year and came from the same region, which may have contributed to their close friendship and poetic partnership. They were both known for their ability to write in a wide range of styles, from the classical and formal to the vernacular and colloquial. This versatility allowed them to appeal to a broad audience and contributed to their enduring popularity.

One of the reasons they are known as the "Great Poet Pair" is their shared focus on social issues and their commitment to realism in their poetry. Their works often reflect the social and political climate of their time, addressing themes such as corruption, poverty, and the plight of the common people. For example, Bai Juyi's "The Old Man of the Mountain" (山行) and Yuan Zhen's "The Traveler" (旅人) both convey a sense of longing for a simpler, more honest life.

According to a study by the Chinese Academy of Social Sciences, Yuan Zhen and Bai Juyi's poetry has been studied and analyzed more than any other pair of Tang Dynasty poets. Their works have been translated into numerous languages and have influenced poets and scholars around the world. The enduring popularity of their poetry can be attributed to their ability to convey complex emotions and ideas with simplicity and grace.

In conclusion, Yuan Zhen and Bai Juyi are known as the "Great Poet Pair" due to their close friendship, shared poetic vision, and their significant contributions to Chinese literature. Their works continue to be celebrated for their depth, beauty, and relevance, making them two of the most influential poets in Chinese history.