What is a paragraph?

A paragraph is defined as a collection of sentences which focus on one key idea. That key idea is introduced and expanded upon in the series of sentences. One of these sentences is known as the topic sentence. In most cases, the topic sentence is easy to identify as it appears as the first sentence of the paragraph, however, it is possible for a topic sentence to appear midway through or even as the final sentence of a paragraph.

A good guide to optimal length of a paragraph is four sentences, but there is no definitive length. The four sentence paragraph allows for - topic sentence, expanding sentence, evidence sentence and concluding sentence. One sentence is certainly not sufficient to fulfil the purpose of the paragraph. Conversely, a ten sentence paragraph may cause the the reader to become confused as to the key point the writer intended to convey.

To check whether you have written an effective paragraph, ask five people to read it and have each of them tell you in five words the paragraph's key idea. If their responses are similar (and close to what you hoped to convey), you'll know your paragraph works. If their answers are all quite different, vague or much longer than a five word summary, that's a sign the paragraph needs revision.

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