Wikipedia:LEAD

The lead is the first part of the article that most people will read. For many, it may be the only section that they read. A good lead section cultivates the reader's interest in reading more of the article, but not by teasing the reader or hinting at content that follows. The lead should be written in a clear, accessible style with a neutral point of view.

The lead should stand on its own as a concise overview of the article's topic. It should identify the topic, establish context, explain why the topic is notable, and summarize the most important points, including any prominent controversies. The notability of the article's subject is usually established in the first few sentences. Like in the body of the article itself, the emphasis given to material in the lead should roughly reflect its importance to the topic, according to reliable, published sources. Apart from basic facts, significant information should not appear in the lead if it is not covered in the remainder of the article.

As a general rule of thumb, a lead section should contain no more than four well-composed paragraphs and be carefully sourced as appropriate.

As explained in more detail below, the lead section may contain optional elements presented in the following order: disambiguation links (dablinks/hatnotes), maintenance tags, infoboxes, foreign character warning boxes, images, navigational boxes (navigational templates), introductory text, and table of contents, moving to the heading of the first section.

Structure of lead section:

The lead must conform to verifiability, biographies of living persons, and other policies. The verifiability policy advises that material that is challenged or likely to be challenged, and direct quotations, should be supported by an inline citation. Any statements about living persons that are challenged or likely to be challenged must have an inline citation every time they are mentioned, including within the lead.

Because the lead will usually repeat information that is in the body, editors should balance the desire to avoid redundant citations in the lead with the desire to aid readers in locating sources for challengeable material. Leads are usually written at a greater level of generality than the body, and information in the lead section of non-controversial subjects is less likely to be challenged and less likely to require a source; there is not, however, an exception to citation requirements specific to leads. The necessity for citations in a lead should be determined on a case-by-case basis by editorial consensus. Complex, current, or controversial subjects may require many citations; others, few or none. The presence of citations in the introduction is neither required in every article nor prohibited in any article.

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Wikipedia