Typically, genres develop to help writers accomplish a general purpose. Informative essays, for example, help writers demonstrate their knowledge to an instructor, while informative articles in newspapers, magazines, and newsletters help writers share information and ideas with their readers. Opinion columns and letters to the editor, in contrast, are often used by writers to advance arguments.

Documents in a particular genre are usually written for the same general purpose. Documents that follow a particular genre also tend to use similar writing conventions, such as level of formality or the type of evidence used to support a point. For example, newspaper obituaries are usually formal and serious, while e-mail messages are often relaxed and informal. Scholarly articles almost always refer to the source of evidence offered to support their points, while letters to the editor sometimes offer no evidence at all. In addition, documents in a particular genre often use similar design elements. Academic essays, for example, are usually written with wide margins and double-spaced lines, while magazine articles often use columns and make extensive use of color and illustrations.

In most cases, genres are social inventions, shaped by the social, cultural, and disciplinary contexts from which they emerge. When writers and readers form a community — such as an academic discipline, a professional association, or a group that shares an interest in a particular topic or activity — they begin to develop characteristic ways of communicating with one another. Over time, members of a community will come to agreement about the type of evidence that is generally accepted to support arguments, the style in which sources should be cited, and how documents should be designed and organized. Over time, the specific needs of a community will result in subtle but important changes to a genre. If you’ve ever read informative articles in magazines for automobile or motorcycle enthusiasts, for example, you’ll notice that they differ in important ways from informative articles in magazines about contemporary music. Similarly, you’ll find important differences in the organization and evidence used in scholarly articles written by such diverse groups of scholars as sociologists, civil engineers, and chemists.

As the needs and interests of a community change, genres will change to reflect those needs and interests. In some cases, a genre will change. Academic essays, for example, might begin to make greater use of color and illustrations. In other cases, a single genre might evolve into several distinct genres. For an example of this, take a look at the Web. As the number of readers on the Web has exploded over the past two decades, Web sites have become far more specialized. In the mid-1990s, most Web sites looked alike. Today, you’ll find characteristic differences among personal blogs, commercial Web sites, government agency Web sites, and entertainment Web sites.

To learn more about genre and design, pay attention to the wide range of documents you encounter in your reading. The most important part of this process is simply being aware that genres exist. By thinking about how writers use different types of documents, you’ll take the first steps toward using genres to achieve your own purposes and consider your readers.