Key Parts of a Paragraph
Your paper will comprise many different paragraphs, but they all will be structured in much the same way. Each usually begins with a topic sentence, followed by supporting details and a summary sentence that ends the paragraph. This is the same whether the paragraph is defining something, comparing two or more things, describing a series of events, or making judgments or evaluations.
The opening sentence introduces the ideas in that paragraph, revealing to the reader what the paragraph is about. It does not have to be a statement; it could be a question or an exclamation. In fact, some variety in your opening sentences will make your paper more interesting to read. Remember that the paragraph's main idea should be stated succinctly when the reader gets to the topic sentence.
The topic sentence can occur anywhere in a paragraph of your research paper. It is often the first sentence, but it does not have to be. It can also occur in the middle of a paragraph, and is sometimes most effective as the last sentence of the paragraph.
All of the other sentences in a paragraph should relate back to that first sentence in some way. They are there to support the idea and to add more detail to it. Take care to keep these supporting sentences focused on the main idea of the paragraph they are in. They should describe the idea more completely, use examples to further illustrate the idea, or explain the reasons for that idea.
Paragraphs can contain any number of sentences. Some paragraphs are only one sentence long, while others may be dozens of sentences long. Overly long paragraphs are difficult to focus and difficult to read, so most instructors suggest that paragraphs be limited to three to eight sentences.
The final sentence of each paragraph summarizes the thoughts of that paragraph. It is often just a restatement of the topic sentence using different words, and it is used to complete the main idea of the paragraph. The last sentence of a paragraph can also contain the suggestion of another related idea, which will be the topic of the next paragraph, of course.