Topic Sentence

Topic Sentence
The topic – easy
What you want to say about the topic is the controlling idea.
Topic sentences should always contain both (1) a topic and (2) a controlling idea

Topic Sentence
When your introduction contains a clearly stated topic sentence, your reader will know what to expect and, therefore, understand your ideas better.

Topic Sentence
Read the following topic sentences.
They all contain a topic and a controlling idea.

Topic Sentence
People can avoid burglaries by taking certain precautions.
2. There are several advantages to growing up in a small town.
3. Most US universities require a 550 point TOEFL score for a number of reasons.

Topic Sentence
4. Air pollution in Mexico City is the worst in the world for a number of reasons.
5. Fixing a flat tire on a bicycle is easy if you follow these steps.
6. There are several enjoyable ways to travel between the US and Queretaro.

Topic Sentence
7. Animals in danger of becoming extinct come from a wide range of countries.
(The different countries… [parts, kinds, types])
8. Effective leadership requires specific qualities that anyone can develop.
(The qualities (or characteristics or traits) of…)

Topic Sentence
9. Industrial waste poured into Lake Michigan has led to dramatic changes in its ability to support marine life.
(The effects of…)
10. In order to fully explore the wreck of the Titanic, scientists must address several problems.
(The difficulties of…) or (The obstacles to…)

Summary
A carefully thought out topic sentence will serve two important functions.
First, it will provide you, the author, the means to stay focused on your objective. It's a lot easier to write if you know what you are going to write about!

Summary
Second, a clearly stated topic sentence will provide readers with the tools they need to clearly understand what you have to say. These are important reasons to carefully consider topic sentences before beginning writing.

Check your version against this sample answer. Notice that the first sentence is the topic sentence
Garlic (Allium sativum L.) has been used for centuries for medicinal purposes. Its use for healing purposes can be traced back as far as 1550BC when documentations of its therapeutic use first appear in Egypt (Hassan, 2003; Rivlin, 2001). In modern times belief in the beneficial effects of garlic on health has led to it being used for a number of conditions. Garlic has been shown to reduce the risk of cardiovascular disease (Aboul-Enein and Aboul-Enein, 2005), and possess anti-microbial (Sivam, 2001) and antioxidant properties (Imai et al., 1994). This essay will explore research into garlic's potential roles in reducing cancer risk and in treating cancer.