Introduction of the General Knowledge
The use of a topic sentence is frequently applied in the selected reading materials for English learners especially university students. As a significant English writing skill, adding an effective topic sentence has several benefits such as linking the whole passage together and giving readers a general idea of the content. Due to its advantages in effective writing, students are often encouraged to master this technique. Their teacher would probably spend a certain amount of time focusing on this specific writing skill.

Definition: A topic sentence is a statement summarizing the main idea of a paragraph. In other words, it tells us what the paragraph is about. Usually, a topic sentence consists of two parts: a topic and its characterization. For example, in this topic sentence: Juliet is a wonderful singer. Juliet here is the topic and wonderful the characterization.

Effect: The effect of a topic sentence can be significant. Through a very simple sentence, readers are rapidly informed of the main content that the writer is going to talk about. Leading off the paragraph, it helps readers grasp the gist of the author’s idea. What’s more, the writer is able to maintain coherence by checking the content of the paragraph with a carefully-selected topic sentence, avoiding adding unnecessary information and being distracted from the main idea as he writes his paragraph. The topic sentence reminds him of what additional information might be added for further explanation supporting his argument. In the same way, with the help of a well-formulated topic sentence, readers are able to predict what he will be informed of in the paragraph.

Standard: The standard of a good topic sentence is diverse, covering several aspects in terms of writing. Precision and specificity come on top of the list. A good topic sentence is also extensive enough to include everything the writer wants to discuss in more detail in the following parts.

Position: There are different positions that a topic sentence may be placed in other than at the beginning of a paragraph though it is the most popular pattern enabling writers to check consistency more conveniently. A topic sentence can also be placed at the head of a paragraph and be repeated at the end of the paragraph. Special emphasis is given to the topic sentence in this way and in some cases it serves as a transition between a comparison and a contrast. The end position of a topic sentence always illustrates the effect of creating a feeling of suspense encouraging readers to keep on reading.
Further Explanation

Identification
Let's look at this example: "I had a beautiful organic garden last summer. First, I composted all of the leaves, plants and food wastes over the previous winter. By springtime, I mixed the compost into the soil, and then planted my favorite vegetables. My family enjoyed picking the crop of our efforts."
The topic sentence tells readers what the paragraph mainly talks about. In this case, the topic sentence of the paragraph above should be "I had a beautiful organic garden last summer", as it expresses the main idea of the paragraph.
Considerations
Topic sentences are followed by several supporting sentences describing the main idea further. It points out the direction of the paragraph and leads its content. The point of view stated in the topic sentence is then enlarged upon through reasons and examples expressed in the other sentences of the paragraph.
Function
It serves as a means for writers to grab main idea and summarize it in the form of a sentence. It lead you to think about your supporting information and what you are actually writing about. When you research your information, always refer to your topic sentence and make note of the most important details of your topic. Finally you can pull the idea together to form a concise, yet comprehensive, statement about your writing assignment.
Features
A paragraph's topic sentence is the "catch line" that captures the reader's attention. It tells readers that this is something worth noticing because this is exactly what the whole paragraph is going to explain and support. The topic sentence acts as a key to unlock the content of the paragraph.
Placement
Usually, topic sentences are placed at the beginning of the paragraph. By writing it at the very first place, the writer is informing the reader of what information will come. However, in case of more creative writings, topic sentences may be placed in the middle or at the end of a paragraph. These occasions occur quite often in essays nowadays.


Paragraphs and Topic Sentences
A paragraph is an combination of sentences that are coherent and organized, and all the sentences providing information should be related to a single topic. Almost every piece of writing that possesses more than just a few sentences should be organized into paragraphs because paragraphs show a reader where the subdivisions of an essay begin and end so as to help the readers sort out the logical development and grasp what the writer tries to convey.

A significant sentence type is topic sentence among all the classifications of sentences like description, narration, compare, contrast and so on.A topic sentence should express a single controlling idea that the following part is going to support. Using a topic sentences has several benefits: a topic sentence substantiates the thesis statement; it links the content of a paragraph and sorts out the order of the sentences; and it quickly informs the reader of the subject to be discussed. Readers generally take a glimpse of the first few sentences in a paragraph to find out the subject and perspective of the paragraph. That’s why it’s often best to put the topic sentence at the very beginning of the paragraph. In some cases, however, it’s more effective to place another sentence before the topic sentence—for example, a sentence bridging the current paragraph with the previous one, or a sentence with background information.

Most paragraphs should have a topic sentence for the sake of clarity and coherence, however, there are a few situations when a paragraph does not have one. For instance, a topic sentence can be left out in a narrating paragraph that shows a series of events, if a paragraph simply develops an idea introduced above in the previous paragraph, or if all the sentences and supporting information in a paragraph refer clearly or sometimes indirectly to a main idea. It is suggested that the vast majority of paragraphs in an essay should have a topic sentence.

Writing Topic Sentences


To write a topic sentence in academic writing, it is important to understand that although topic sentences may appear anywhere in a paragraph, in formal academic essays they are more often placed at the beginning.
A topic sentence relates the paragraph to the essay's main idea, and thereby serves as a signpost for the argument of the paper as a whole, but it also defines the scope of the paragraph. For example, consider the following topic sentence:

Many fast-food chains make their profits from adding a special ingredient called "forget sauce" to their foods.

If this sentence controls the whole paragraph, then all sentences in the paragraph must focus on key words such as fast food, profit, and "forget sauce":

Made largely from edible oil products, this condiment is never listed on the menu.

This sentence fits in with the topic sentence because it goes on with the description "forget sauce."

In addition, this well-kept industry secret is the reason why ingredients are never listed on the packaging of victuals sold by these restaurants.

This transitional phrase "In addition" relates the composition of "forget sauce" to secret fast-food industry practices.

"Forget sauce" has a chemical property which causes temporary amnesia in consumers.

Now the paragraph moves on to the short-term effect on consumers:

After spending too much money on barely edible food bereft of any nutritional value, most consumers swear they will never repeat such a disagreeable experience.

This sentence describes its longer-term effects:

Within a short period, however, the chemical in "forget sauce" takes effect, and they can be depended upon to return and spend, older but no wiser.

Finally, the paragraph is finished by bringing forth the claim contained in the topic sentence, that many fast-food chains make their profits from adding a special ingredient called "forget sauce" to their foods.

Analysing a Topic Sentence

To some extent, topic sentences are rather similar to tiny thesis statements. Like a thesis statement, a topic sentence makes a claim that the writer is going to argue about in the paragraph. As the thesis statement is the unifying force in the essay, so the topic sentence must be the unifying force in the paragraph. Further, as is the case with the thesis statement, when the topic sentence makes a claim, the paragraph which follows must expand, describe, or prove it in some way. Both thesis statements and topic sentences put forward a viewpoint first and then bring forth supporting details.

Consider the last paragraph about topic sentences, beginning with the topic sentence itself:

To some extent, topic sentences are rather similar to tiny thesis statements.

This is the claim, or the point that is going to be proved in the following paragraph. All the sentences that follow this topic sentence must relate to it in some way.
Like a thesis statement, a topic sentence makes a claim that the writer is going to argue about in the paragraph.As the thesis statement is the unifying force in the essay, so the topic sentence must be the unifying force in the paragraph.

These two sentences show how the reader can compare thesis statements and topic sentences: they both make a claim and they both provide a focus for the following writing.

Further, as is the case with the thesis statement, when the topic sentence makes a claim, the paragraph which follows must expand, describe, or prove it in some way.

Using the transitional word "further" to relate this sentence to those preceding it, the idea is expanded on the topic sentence in the suggested ways a topic sentence can be related to the following parts.

Topic sentences make a point and give reasons or examples to support it.

Finally, the paragraph is wrapped up by reiterating the main idea of the paragraph.



More Examples

In many cases, topic sentences are not suitable for all kinds of writing, and not all paragraphs need a topic sentence. Paragraphs that describe, narrate, or detail the steps in an experiment do not usually need topic sentences. But there is no doubt that topic sentences are useful especially in paragraphs that analyze and argue. For writers who have difficulty developing focused, unified paragraphs and tend to sprawl a lot, the application of topic sentences are a must. They help these writers develop a main idea and choose coherent supporting information to write in the paragraph. Perhaps most significantly, they help these writers stay focused and keep paragraphs manageable.

On the other hand, topic sentences are also useful to readers who can be guided through complex arguments. Many experienced writers effectively apply topic sentences to connect paragraphs. Here's an example of how one professional writer does this:

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The first part of the topic sentence here — Soon after the spraying had ended — is a transitional clause that refers back to the previous topic: DDT spraying. Topic sentences often begin with such transitional clauses referring to the previous paragraph. The second part of the topic sentence — there were unmistakable signs that all was not well — shapes and leads the upcoming content. This kind of bridging helps the reader follow writers' argument. Carson further helps the reader follow her point by offering them a more condensed version of the topic sentence later — All the life of the stream was stilled. This sentence tells us exactly what Carson meant by all was not well.



External Links
http://owl.english.purdue.edu/owl/resource/573/01/
http://homepage.ntu.edu.tw/~avwrite/exercises/topicsentence.htm ( This link is strongly recommended by the page contributor for It contains exercises which are well designed and beneficial to learners.)
http://www.rrcc.edu/writing/topic-thesis.html
http://www.brighthub.com/education/k-12/articles/15419.aspx


References
http://www.writing.utoronto.ca/advice/planning-and-organizing/topic-sentences
http://grammar.about.com/od/tz/g/topicsenterm.htm
http://www.mce.k12tn.net/reading39/paragraph_unit/lesson4.htm
http://www.writingcentre.uottawa.ca/hypergrammar/partopic.html
http://lsa.colorado.edu/summarystreet/helptext/topic.html
http://www.indiana.edu/~wts/pamphlets/paragraphs.shtmlhttp://www.englishclub.com/writing/index.htm http://www.ehow.com/about_4777518_topic-sentence_.htmlhttp://www.eslbee.com/topic_sentences.htm
http://grammar.ccc.commnet.edu/grammar/paragraphs.htm
Active Skills for Writing, Foreign Language Teaching and Research Press, 2003A New English Course, Students' Book, Shanghai Foreign Language Education Press, 2008