. | 1. | a proposition stated or put forward for consideration, esp. one to be discussed and proved or to be maintained against objections: He vigorously defended his thesis on the causes of war. |
| 2. | a subject for a composition or essay. |
| 3. | a dissertation on a particular subject in which one has done original research, as one presented by a candidate for a diploma or degree. |
| 4. | Music. the downward stroke in conducting; downbeat. Compare arsis (def. 1). |
| 5. | Prosody.
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| 6. | Philosophy. See under Hegelian dialectic. |

The central idea in a piece of writing, sometimes contained in a topic sentence.