Who can tell me what is the rhyme of poetry? Includes five words, seven words.

Ancient Chinese has four tones (one flat, two rising, three turning points and four falling tones), which are called "flat, rising, rising and falling" respectively. Flat tone and rising tone are flat tone, and rising tone and falling tone are flat tone. Taking Qiyan as an example, the second, fourth and sixth sentences require that "two (flat) orioles sing green (flat) willows, and a row of (flat) egrets (flat) ascend to heaven". Then the vowels of the last word of each couplet should be consistent, which is called rhyme. The first, second and fourth parts (the first part, the second part and the last part) (eight clauses, each of which is called a couplet, followed by "the first part, the coordinate part, the neck part and the last part") of a metrical poem require rhyme, and the third part (the neck part) can be handled flexibly.