What Is a Topic Sentence?
Imagine you've walked into a party knowing nobody. You make yourself a drink, look around the room, and spot another person, silently standing there, sipping his or her drink, and surveying the scene. He or she looks like a nice person, but what are you going to say? It might be something as simple as 'Hello, my name is Eva' or 'I really love your red sweater' or 'What do you think of all the food?' Whatever you decide to say, it will contain the main idea and focus of the conversation and tell the other person what that initial conversation is going to be about. It will be your topic sentence.
In writing, the topic sentence is the main idea of each paragraph. It contains the focus of the paragraph and tells readers what the paragraph is going to be about. Although the topic sentence can be located anywhere in a paragraph, in academic essays, it is usually located at the beginning of each paragraph.