Paragraph unity is the most important characteristic of a good paragraph. It defines that all sentences in a paragraph should speak about one single idea or one main subject. That is, the topic sentence, the supporting details, and the concluding sentence should focus on only one idea. Further, paragraphs should also be coherent. Coherence demands that the ideas or sentences presented in a paragraph should flow smoothly from one to the other. Paragraphs should not only be well-developed and unified but also coherent. In this lesson you will learn about paragraph unity and coherence without which a paragraph cannot be called a complete composition.