The "key concept" being expressed. A STATEMENT about the topic that conveys the overriding theme of most—if not all—of the remaining sentences in a paragraph. The main idea provides the message of a given paragraph or the argument that is being made about the topic. It may be implied or directly stated, but you must state it in a complete sentence.
Ask yourself: What is the overall message or argument being made regarding the topic of this paragraph or essay? Certain words or word combinations often introduce the main idea: in short, in brief, in summary, in fact, clearly, thus, as these examples show.
The main idea may be stated at the beginning of the paragraph, in the middle, or at the end. The sentence in which the main idea is stated is the topic sentence of that paragraph.
Sometimes main ideas are expressed in two sentences, and sometimes a single main idea will serve for two paragraphs. Main ideas can be unstated, or implied, requiring that you infer the main idea.
Specific information about or support for the main idea. Details, major and minor, support the main idea by telling how, what, when, where, why, how much, or how many.
Topics, main ideas, and supporting details WORK TOGETHER; the main idea makes an argument about the topic, the details offer support for the main idea.
To please: to delight, entertain, amuse, give pleasure to, describe, paint a picture in words. To instruct: to teach, show, inform, examine, expose, analyze, criticize. To persuade: to convince, change one's mind, influence, argue, recommend, give advice to.