Paragraphs should have unity and structure.
Each paragraph should be unified: it should be about one single thing or idea.
When a new idea—or a new aspect of an idea—begins, begin a new paragraph.
A topic sentence indicates the main idea that unifies the paragraph, just as a thesis statement gives the main idea of an essay or article.
Paragraphs in one piece are generally about the same length, which is proportionate to the length and complexity of the piece of writing.
Paragraphs can occasionally be one sentence for special emphasis, but they are usually several sentences long.
To learn more, see:
Transitions move your reader smoothly from one idea to the next and clarify the relationships between your points.
Transitions are words or sentences that show your reader how your ideas and points relate.
Sometimes ideas flow together obviously.
Other times you need to explain the logic of the relationships, use repeated terms, or employ other transitional devices so your readers will not be startled or confused.
To learn more, see: