2. The content is opposite. For example, the window contains autumn snow in Xiling, and the Wu Dong Wan Li boat is moored at the door. Doors and windows, Xiling-Wu Dong, Qian Qiu-Wan Li and Sesshū Tōyō are all opposite. Only drink Changsha water and eat Wuchang rain. Only-come again, drink-eat, Changsha-Wuchang, water-fish. They are all against each other.
3. rhyme. Ancient poetry pays attention to rhyme. Generally, it is four sentences and one rhyme (except some epigrams), and four sentences are a short paragraph.
China's folk poems are generally free. The content is substantial.