All compositions consist of literary units called paragraphs. A paragraph develops a main idea, which is stated in a topic sentence. Functioning in a paragraph in the same way that a thesis statement functions in an essay, a topic sentence establishes the direction for the paragraph, with all other sentences in the paragraph supporting and developing it.
Although a topic sentence often appears at the beginning of a paragraph, it may also be placed in the middle or at the end. When it is placed at the beginning of the paragraph, the rest of the sentences support the topic sentence, and the paragraph is developed deductively. In other words, the main idea appears first, then the information supporting this idea follows. For example:
For my family, Sunday is undoubtedly the best day of the week. We get home from church around 12:30. After a late lunch the day seems to stretch before us unendingly. Usually, my brothers and I leaf through the extra-thick Sunday paper (with full-color comics!) for a while, and then postpone our homework, choosing to nap or go for a ride instead. Occasionally, there’s an old movie worth watching on television, or at least a golf tournament, which my dad snores through on the recliner in our warm living room. And, of course, it’s always nice just to sit in the shade with a Coke or lemonade while the afternoon floats by.
Sometimes the topic sentence occurs at the end of the paragraph. When this is the case, the topic sentence provides the focus for the sentences leading up to it. The paragraph is developed inductively; that is, the evidence is given first, and then the conclusion derived from this evidence is stated. For example, the following paragraph is about the Texas Hill Country:
Settlers soon discovered that the streams of East Texas were full of fish. The hills were full of game. There were, to the experienced eyes, all the signs of bear, and you didn’t need signs to know about the deer—they were so numerous that when riders crested a hill, a whole herd might leap away in the valley below, white tails flashing. There were other white tails, too: rabbits in abundance. And as the men sat their horses, staring, flocks of wild turkeys strutted in silhouette along the ridges. Honeybees buzzed in the glades, and honey hung in the trees for the taking. Wild mustang grapes, plump and purple, hung down for making wine. Wrote one of the first men to come to the Hill Country: “It is a Paradise.”
Robert A. Caro - The Path to Power
Sometimes the topic sentence is delayed until the middle or near the middle of the paragraph. When this is the case, the topic sentence serves as a bridge, or transition, between the information in the first part of the paragraph and the information in the second. For example:
History is always written by the victors. The basic Tudor picture of Richard as a bloodthirsty tyrant was handed down through the standard histories of England and the school textbooks for five centuries. There has been an obstinate opposition, however. Beginning with Sir George Buck in the 17th century, a series of writers and historians have insisted that Richard was not getting a fair break, that the Tudor version was largely fabrication: far from being a monster, Richard was a noble, upright, courageous, tenderhearted and most conscientious king. This anti-Tudor version reached its definitive statement in the work of Sir Clements Markham, a 19th-century eccentric who spent years of passionate research trying to prove that crimes attributed to Richard were either outright libels by, or the actual work of, a pack of villains, most notably including Cardinal Morton and Henry VII.
Robert Wernick – “After 500 Years, Old Crookback Can Still Kick Up a Fuss"