topic sentence & main idea的分別?

A sentence containing the main idea of a paragraph is called a topic sentence. One or more sentences containing the main idea of an essay is called the thesis.

In many essays, the main idea of the essay can be found in the opening or ending paragraph, and the first sentence of a paragraph is the topic sentence.

For example, an essay with a title of "My dog" may have the main idea "my dog is my best friend" presented in the opening paragraph, which may have a topic sentence of "My best friend is not a human". The second paragraph may have a topic sentence of "Who will wait up for me if I come home at 2am ?", and the rest of the paragraph will identify "who", and will back up the claim with examples.

The summary of the main ideas contained in the topic sentence of each of all the paragraphs of an essay is the main idea of that essay.