Definition : a main idea or meaning in a form of media, usually, a theme is never directly stated.
Examples: The theme of James Cameron's Avatar is to be kind to nature, and take care to preserve it. The theme of the video game Cave Story is to stray away from the easy way out, to persevere through the hardest trials.
Quote: "...what makes things break up like they do?" (p139). This quote shows one of the themes of this book: that no matter how hard we try, all civilizations will fall eventually.