What is difference between topic sentences and introductory sentences?
A topic sentence is a sentence that expresses the main idea of a paragraph, while an introductory sentence is the first sentence of a piece of writing that introduces the topic or sets the tone for the rest of the text. In essence, a topic sentence is a specific type of sentence that serves a certain function within a paragraph, while an introductory sentence pertains to the broader function of starting a piece of writing.