The so-called rhyme in poetry is roughly equal to the so-called vowel in Chinese Pinyin. As we all know, when a Chinese character is spelled with pinyin letters, there are usually initials and finals. For example, the word "q iu" is spelled Qiu, where Q is the initial and iu is the final. The first letter is always in front and the vowel is always in the back. The word "l iu" is spelled as l iu, where l is the initial and iu is the final. So it's a homophone, and the rhyme is iu.
If a matching word is found, the vowel after it is iu.