A paragraph contains sentences about a single topic. It has three main parts: a topic sentence, supporting sentences, and a concluding sentence. The topic sentence introduces the topic. Supporting sentences provide details and examples about the topic. The concluding sentence restates the main point or summarizes the paragraph. Paragraphs should be formatted with an indentation for the first sentence of each paragraph and double spacing between lines. Strong paragraphs maintain focus on a single topic throughout and arrange sentences logically.