A paragraph is a group of sentences that discuss or support one main topic or idea. It may be short or long, but it needs to be able to develop its main idea clearly with enough support. A paragraph may stand by itself, but usually it is part of a longer piece of writing such as an essay or a report. In general, a paragraph will have a topic sentence and supporting sentences, and it sometimes has a concluding sentence. When beginning the next paragraph, you should have a transition to the next idea to make your writing flow smoothly.