To write a good paragraph in communication, the writer first needs to decide upon his purpose or idea and tries to make it clear to his reader in a topic sentence. Then, almost immediately, his idea should be developed by presenting relevant supporting details. After that, the idea just discussed in the paragraph usually needs a logical conclusion to satisfy the reader psychologically. All this, along with various means of paragraph development, helps to organize an overall structure of a paragraph of unity.

Now, examine the sample below to see how the topic sentence (TS) establishes the focus, how the developing sentences (DS) present the supporting details, and how the concluding sentence (CS) summarizes the main idea.

Sample:
Recent awareness of the energy shortage in America has brought the bicycle into renewed popularity. (TS) Citizens who own bikes find themselves pedaling to work and school rather than getting the car out of the garage. Owners of bicycle sales-and-repair shops find their business booming. Many cities have set aside "bikeways" for the convenience and safety of cyclists. Police reports show bicycle theft growing, and sellers of padlocks and chains for bike protection are making new profits. (DS) More and more Americans are discovering that pedal-pumping is cheaper than gas-pumping and that bicycles don't make smog. (CS)