Topic Sentence at the Beginning and the End of the Paragraph
Traditionally the topic sentence is the first sentence of the paragraph. In this lead position, it functions to introduce the examples or details which will explain the controlling idea. If the paragraph is meant as a freestanding unit of discourse and not part of a larger whole, the topic sentence, or rather the ideas it contains, are frequently restated at the end of the paragraph. In this position, the restated topic sentence serves as a concluding statement. Such repetition of the topic helps the readers to follow the content of the paragraph, especially if that content is complex in nature.
A diagram of this type of paragraph development might take the form of an hourglass, where the topic sentence and its restated counterpart form the broad base and top, and the supporting details occupy the intervening space.
The following sample paragraph is one that has a topic sentence at the beginning and at the end of the paragraph:
Throwing a clay pot, the age old art of making pottery on a wheel, is a process that requires many steps. Assuming the potter does not have to make his own clay, the first step toward the finished product is wedging the clay. Here, the potter kneads the clay to prepare it for throwing. Wedging cannot be rushed. A minimum of fifty turns is required to rid the clay of air pockets and align its molecules. Once wedged and formed into a ball, the clay is thrown onto the center of a potter's wheel. Now the material must be centered. Centering not only takes strength but time as well. The clay must be coerced into a perfectly symmetrical shape, dead center on the spinning wheel. To proceed with poorly centered clay is to court certain disaster in the form of tilting, uneven pots, or worse, the total collapse of the piece. When correctly centered, the clay is ready to be opened. To do this, the potter finds the center of the clay and slowly sinks a rigid finger into the still-spinning clay. Only now can the clay be shaped. With a steady but gentle hand, the potter pulls up the sides of the pot until the desired height is reached. Now the shaping is completed and the pot is ready to be dried, fired, and glazed. Thus, even though a clay pot may appear simple to make, fashioning one by hand is a long and sometimes tedious process.
The concluding sentence of this paragraph reminds the reader of the controlling idea of the paragraph, namely that throwing a pot requires many steps. Note that the first and last sentences, while similar, are not identically phrased.
Topic Sentence at the Beginning of the Paragraph
Concluding remarks of a paragraph do not always restate the topic sentence and, in fact, in some paragraphs may be missing altogether. However, a topic sentence is still needed. A second and also common placement for the topic sentence is in the lead position with no repetition in the last sentence.
A paragraph of this nature starts with a strong, general topic statement with subsequent supporting details narrowing from this broad beginning. Such a structure provides the reader with immediate knowledge of the topic and scope of the paragraph and thus serves as a map for the details that follow. This type of structure is most frequently found in newspaper articles, where the headline may also assume the role of topic sentence. A diagram of this paragraph type would be the top half of the above hourglass, or an inverted triangle.
The following sample paragraph begins with a topic sentence. The details which follow it repeat the controlling idea of the paragraph and are arranged in chronological order, that is, from first to last:
Constructing a wedding cake is a complicated process. Before any baking takes place, the size of the cake and the decorative design to be used must be determined. Then the layers are baked. On a large cake the bottom layers may be as much as sixteen inches in diameter. Because of their size, these layers must be baked one at a time, a process which may actually take an entire day. Once the layers are cooled, same-size pairs are matched and frosted. Since large wedding cakes are surprisingly heavy, half-inch dowel rods must be measured, cut, and carefully driven into the bottom layers. These wooden posts provide hidden support for the weighty upper layers. When all the layers are set in place, flowers, garlands and leaves of frosting are added. These delicate touches individualize the wedding cake and transform it from merely a cake into a culinary work of art.
In the paragraph above, the topic sentence is Constructing a wedding cake is a complicated process. The steps involved in constructing this type of cake are told in time order, beginning with baking and ending with decorating. Note that, although the paragraph draws to a logical conclusion, the topic sentence is not repeated in the end position.
Topic Sentence at the End of the Paragraph
While it is most common for topic sentences to begin the paragraph, they do not always do so. Consider the following sign, seen in the window of a beauty salon:
Unless they are booked for service,
In this situation, No exceptions is clearly not the topic of the sign, and No Children clearly is. Yet the subject, No Children, is placed in the end rather than the head position. When this idea is extended to the paragraph, the topic sentence, placed last, serves to summarize the previous details. Paragraphs written in this way can be diagrammed as an upright triangle, with the broad base representing the topic sentence:
Paragraphs are written in this form primarily for one of two reasons: (1) to create suspense or (2) to bring up a controversial topic only after sufficient groundwork has been laid. In the case of the sign in the beauty salon, the message is made gentler by stating the only situation in which children are allowed before stating the more controversial behest, No Children, in the final position. The act of providing convincing data or groundwork leads the reader to the topic sentence, which then also serves as the conclusion.
The following sample paragraph is an example of one in which the topic sentence and controlling idea appear in the final position:
People do it everyday. They log on to their favorite website and browse for hours, checking out bargains. They dump every possible wish into their shopping carts, knowing they can cast each one aside before they finalize their purchases. On the way, they may enter a sweepstakes in the hopes of winning a trip to Cabo San Lucas, or maybe even a new SUV. And then, when they have decided on their purchases, they enter private information without giving it a thought. With a keystroke, they release their personal data into what may or may not be a secure zone. Despite what much of the public believes, internet shopping is not safe.
In this paragraph, the idea that internet shopping may not be safe could be considered controversial. For this reason, groundwork is laid before the final, topic sentence is stated.
Topic Sentence in the Middle of the Paragraph
Perhaps the least common placement for a topic sentence is in the medial position. Placed here, a topic sentence can provide a transition between two kinds of details, those appearing before the topic sentence and those appearing after it. In this paragraph structure, the controlling idea may be of a cause/effect or comparison/contrast nature. The topic sentence, then, serves the function of linking sets of related but different data. A paragraph of this type can be diagrammed as a diamond with details at both ends and the broad, topic sentence in the middle.
The following is a sample paragraph with the topic sentence in the medial position:
When a camera flash is used in a low-light environment, the subject's eyes may appear red in the finished photograph. What is known as "red-eye" is the result of light from the flash reflecting off the pupils of the eyes. The phenomenon of red-eye can be lessened by using the red-eye reduction feature found on many SLR cameras. This feature activates a lamp which shines a small light directly into the subject's eyes. When this happens, the diameter of the pupil is reduced, thus tightening the opening in the iris. Since a smaller pupil means a smaller host for the reflection, the chances of red-eye occurring are greatly reduced.
In the above paragraph, the topic sentence is The phenomenon of red-eye can be lessened by using the red-eye reduction feature found on many SLR cameras. It serves to connect information about the cause of red-eye (found at the beginning of the paragraph) with information about how the problem can be alleviated (found after the topic sentence).