The second feature of unity is that every supporting sentence must directly explain or prove the main idea. For example, in a paragraph about the high cost of prescription drugs in the United States, you could mention buying generic brands as an alternative to brand-name drugs, but if you write several sentences about how generic drugs are made, you are getting off topic, and your paragraph will not have unity.
COHERENCE
Although paragraph unity is important, it is not the only factor that you need to consider in writing a successful paragraph. In order for paragraphs to be well-structured, they must also be coherent. The word coherence comes from the Latin verb cohere, which means "to hold together." For coherence in writing, the sentences must hold together; that is, the movement from one sentence to the next must be logical and smooth. There must be no sudden jumps. Each sentence should flow smoothly into the next one.
Here are four ways to achieve coherence:
• Repeat key nouns.
• Use consistent pronouns.
• Use transition signals to link ideas.
• Arrange your ideas in logical order.