2. Language evolution: Language is a lively substance. With the constant evolution and change of users, the language is also evolving and changing. As a language form, the language of ancient poetry has also been influenced by the language evolution, and the language form has also changed.
3. Modification and processing: In ancient times, many ancient poems may have been passed down from mouth to mouth. With the passage of time, different people may have modified and processed ancient poems and changed their language forms.
4. Copying errors: Copying ancient poems mainly depends on handwriting, and there may be copying errors, which will lead to changes in the language form of ancient poems.