A paragraph is a group of about 6-12 sentences expressing a main idea. It can give information tell an opinion, explain something, or even tell a short story. Every sentence in a good paragraph is about the same topic. All of the sentences, which are arranged logically, so the reader can easily understand what the writer wants to say, explain the writer’s main idea (most important idea) about that topic. When the writer wants to write about a new main idea, he/she begins a new paragraph.
In academic writing, a paragraph is usually built up by two types of sentences. The first type is called the topic sentence, which directly tells the reader what the paragraph is about (topic). It states the main idea. It is usually (but not always!) placed in the beginning of the paragraph. The second type is called supporting sentences. They give more information about the topic. They add specific details and explanations. If the supporting sentences directly explain the topic, they are called major supporting sentences. If they explain the topic indirectly (by supporting a major supporting sentence, they are called minor supporting sentence, In addition to the topic and supporting sentences, some paragraph can also have a concluding sentence. It restates the main idea (in a different way from the topic sentence) or presents a final comment about the topic.
Look at the following sample.
(1) Computer chips have changed our way of life in many ways. (2) With computer chips we can make very small computers. (3) Space scientists use these small computers in satellites and space ships. (4) Large companies use these small computers for business. (5) We can make very small calculators with computer chips. (6) Some calculators are as small as a credit card, and these calculators are not very expensive. (7) Computer chips are also used for making digital watches. (8) A normal watch has a spring and moving hands, but a digital watch has no moving parts. (9) A digital watch show the time and date with numbers, and some digital watches even have and alarm and a stopwatch. (10) The computer chip makes all of this possible.
Sentence 1 is the topic sentence. Sentences 2, 5, and 7 are major supporting sentences. They directly explain the topic sentence. Sentences 3 and 4 support sentence 2. Sentence 6 explain sentence 5. Sentence 8 and 9 support sentence 7. Therefore, sentences 3, 4, 6, 8, and 9 are major supporting sentences. Sentence 10 is the concluding sentence. It restates the main idea.