Rhyme has strict rules in terms of words, rhymes, even words and antithesis, and the common types are five-character metrical poems and seven-character metrical poems. Metric poems originated from Shen Yue and other new-style poems that emphasized the antithesis of metrical poems in the Southern Dynasties, and were further developed and stereotyped by Shen Quanqi and Song Wenzhi in the early Tang Dynasty, which prevailed in the Tang and Song Dynasties.