How to Write Topic Sentence

Topic sentence introduces the topic or main idea of the paragraph. It is usually the first sentence.  A good topic sentence should not be too broad or too narrow.

A good topic sentence must include one topic and one controlling idea.

• Topic: A topic is what you want to write about. 
• Controlling idea: Controlling idea limits what you will write about. It is the limit of supporting ideas you will include in your paragraph. 

Thus, we can say:

TOPIC SENTENCE = TOPIC + CONTROLLING IDEA

Look at the examples below. The topics are in red, controlling ideas are in blue. 


  • There are three disadvantages of mobile phone.
  • Angkor Wat is attractive for a few reasons.
  • Poverty is caused by four main factors.
  • Vutha is a hard-working student.
  • Internet revolutionizes the way we works in three ways.