Question

One of the main differences between central idea and theme is
Theme is found when you have one main character, central idea is limited to stories with multiple characters.
Themes are explicitly stated and central ideas are not.
Central ideas can only be found only in narrative writing, while themes can be found in multiple types of literature.
Central idea can be found in both fiction and nonfiction texts.

Answer 1

A theme is a universal lesson learned and the central idea is a one-sentence main idea.

Central idea conveys that the text is about mainly, whereas, theme refers to the author's message, life lesson or moral learned from the story.

A central idea cannot be referred to as the topic of the text, on the other hand, a theme cannot be same as topic.

In one sentence, the central idea can be stated, whereas, themes are repeated and can be multiple.

A theme is not the central idea, nor it can act as a topic of the text.

therefore, the main difference between central idea and theme is theme is found when you have one main character, central idea is limited to stories with multiple characters.