In poetry, what term refers to the underlying message or meaning the writer is trying to convey?

The term that refers to the underlying message or meaning in poetry is theme. The theme encompasses the central ideas or insights about life, society, or human nature that the poet wishes to communicate. This can include various interpretations and emotional responses that arise from the work, allowing readers to connect on a deeper level with the material.

While "concept," "content," and "message" are related terms, they do not specifically capture the broader, more universal understanding that the theme provides. The concept might refer to a specific idea or an abstract notion within a piece, while content is generally about the subject matter itself—what is literally presented in the poem. Message, while closely aligned with theme, can be more direct and may not convey the thematic depth that encompasses the overall meaning and emotional resonance aimed for in a literary work. Thus, theme is the most accurate term for referring to the underlying meaning in poetry.