Generally: 1. Enhance emotional appeal. 2. Suitable for the theme content that the poem wants to express. 3. For the purpose of confrontation or display of literary talent, etc. Analyze the specific situation in detail, such as: The word "green" in: The spring breeze turns green on the south bank of the Yangtze River
, 1. vividly shows the green scenery of the south of the Yangtze River in spring. 2. The contrast with the next sentence highlights the pain in the author's heart and enhances the emotional appeal.