It affects the mood, which affects how theme is interpreted by the reader.
The diction is simply the choice of words the writer used in the story. This easily distinguishes a good from a bad writing. The words used in a literature should be accurate and appropriate on the context of idea that is being used to therefore, the diction affects how the theme of the story is being received by a reader. The reader’s interpretation of the theme of the story will be influenced by the choice of words used in constructing the story.