Just as it is hard to formulate a satisfactory definition of a sentence, so it is difficult to define a paragraph. Perhaps the easiest way to identify a paragraph is visually--as a group of sentences set off from other groups of sentences by an indentation of its first line:

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Though a paragraph may be only one sentence long, it is usually comprised of several sentences which develop one idea, one point, or one aspect of a subject. Very often this idea or subject is stated in a topic sentence, a sentence which focuses the paragraph. The topic sentence is usually the first sentence of the paragraph, but it may come at the end or even in the middle of a paragraph. Furthermore, a long paragraph may have several sub-topics, each introduced by its own 'subtopic' sentence. Sometimes a paragraph may have no topic sentence if it is organized around a theme that the writer has in mind but does not state explicitly. Even if a paragraph has no explicit topic sentence, however, it should have a clear focus.

Paragraphs are most often used to mark the introduction of a new idea or a new section in a piece of writing. However, they are sometimes used to break up long sections of writing into shorter, easier to read pieces. How to break up an essay into paragraphs depends upon the organization and relationship of ideas or information in that peice of writing. Indeed, most writing can be divided into paragraphs in several different ways.

Three essential qualities of a good paragraph are unity, development, and coherence. A unified paragraph develops one main point, with all the sentences relating to that point. A developed paragraph includes sufficient explanation and support of its point for the reader to understand it fully. A coherent paragraph develops its point in an organized, logical way, showing the sequene of ideas and the connections among them.

The chief function of an introductory paragraph is to introduce the topic and present the main point or the thesis of an essay. This point or thesis may be a single sentence which states the main idea the essay will develop or it may be several sentences long, not only stating a main idea, but also indicating the main divisions of an essay and/or outlining the proposed metheods of development.

An effective introduction must interest the reader, introducing the subject under discussion in a way that will convince the reader that the essay will be worth reading. An introduction may do any of the following:

• narrate an anecdote that relates to the subject of the essay. The annecdote may be humorous or serious, but it should involve you reader immediately in a story which suggests the issues to be discussed in the essay.
• cite a quotation and discuss its relevance to the topic.
• describe historical background relevant to the topic.
• describe the current situation in the area of interest.
• describe a person, place, or object relevant to the topic.
• explain special terminology to be used in the essay.
• explain the assumptions about the subject of the essay.

Transitional paragraphs connect sections of an essay. They may summarize a preceding section briefly and introduce a new section, or they may show some logical connection between sections, much as transitional words do between sentences. Transitional paragraphs are usually quite short, sometimes only a sentence in length. They are most often used in longer essays that develop several complex issues.

In shorter essays, the transitional function is usually served by a transitional word, phrase or sentence at the end of one paragraph or the beginning of the next paragraph.

Concluding Paragraphs

A concluding paragraph brings an essay to a close, leaving the reader with a sense of completion. Often, the conclusion will restate the thesis of an essay, sometimes reformulating the thesis in light of the evidence presented in the essay. But concluding paragraphs may work in other ways. If the essay deals with a subject which can be approached in several ways and the essay has chosen one approach over others, the concluding paragraph may defend that approach. A particularly effective kind of concluding paragraph demonstrates the larger implications of a thesis by placing it in the context of some larger issue. Finally, a concluding paragraph may speculate about future developments.