Subject sentences can additionally help you create certain your paragraphs are unified . Each paragraph ought to be about just one thing . If you have any phrase in a paragraph that is perhaps not on subject, it must either be relocated to the paragraph where it belongs, or trashed. The whole paragraph has to go if nothing in the paragraph can be clearly related to your essay’s main idea. Your system paragraphs must all work to prove your thesis: this will make your essay coherent .