The definition of a topic sentence is a sentence that gives the primary idea of a paragraph.
An example of a topic sentence is a sentence that states an opinion which is then discussed and detailed in the paragraph.
the principal sentence, setting forth the main idea and coming usually at the beginning, in a paragraph or other distinct section of a piece of writing, esp. expository writing
The sentence within a paragraph or discourse that states the main thought, often placed at the beginning.
(plural topic sentences)
- A sentence at the beginning of a paragraph indicating the general matter to be discussed later in that paragraph.