theme

In music, a basic melody or musical figure, which often occurs with variations.

theme

In literature, a recurring idea or image in a novel, play, or other text, usually important evidence of the intention of the work. The theme is not the same as the story or plot. For example, a story about a man who regrets some action in his past that led to the death of a friend could have a theme of guilt, even if the word was never mentioned in the story.