How to Identify the Topic & Controlling Idea in a Sentence

What is a topic sentence? The topic sentence gives a paragraph direction and purpose. It shows what the paragraph is about while the controlling idea indicates how the writer will develop that topic idea. Being able to identify these key ideas in a topic sentence will help you read with more understanding because you better know the paper's focus. The process may also improve your own expository and academic writing as you come to understand and see modeled how to write a topic sentence in your own papers or essays.

First, read the topic sentence and make sure you understand it. If you don’t know what the controlling idea sentence is saying or what it means, you may have a hard time identifying its topic and controlling idea. If the topic sentence you are analyzing is not isolated or identified as part of a grammar worksheet, read the entire paragraph to which the sentence is connected. By looking at the entire paragraph, you may be able to distinguish context clues that direct you to easier identification and comprehension of the topic sentence.

Next, identify the subject and nouns of the topic sentence. Most often the topic of a topic sentence is its subject. For example, “The Colorado mountains are the most beautiful in America.” "Colorado mountains" is the subject of the sentence and the topic of this topic sentence. When a topic sentence begins with the pronoun “there” or “it,” look for the element that "there" or "it" is substituting for. For example: “There are beautiful mountains in Colorado” is equivalent to “Beautiful mountains are in Colorado.” Hence, "beautiful mountains" is identified as the topic sentence.

Finally, identify the controlling idea. The controlling idea is either an opinion that needs to be proven or an idea that leads to a list of things that need to be developed. Controlling statement examples like, “Colorado has the most beautiful mountains” is an opinion. Someone may think that Montana or Tennessee has more beautiful mountains. Asking “how do you know?” can help identify the controlling idea of an opinion-based topic sentence. Identifying lists requires a “What are…” question. For example, “The life cycle of a frog has two stages.” What are the two stages? This question then leads to a list. "The life cycle of the frog" is the topic, and "has two stages" is the controlling idea. Thus, the remainder of a paragraph with this topic sentence would discuss each of the two stages of a frog’s life cycle.

After looking at topic sentence examples, continue practicing that process. Identifying the topic and the controlling idea of a sentence may not be easy at first. With practice, it can be more of an automatic process. There are also many practice exercises and quizzes online like grammar-quizzes.com that can help you work on the process.