Finding the Main Idea: Reading Comprehension Review Study Guide

Updated on Aug 24, 2011

Practice exercises for this study guide can be found at:

Finding the Main Idea: Reading Comprehension Review Practice Exercises

Just like speaking, writing is a form of communication. When you read a passage, the author of that passage is trying to tell you something. Otherwise, why would he or she go to the trouble of writing it? What the author is attempting to communicate to you is called the main idea of the passage. Simply put, the main idea is what a passage is mostly about!

Remember the question words in the previous chapter? Well, now's the time to think about that why question: Why is the subject of the passage even being discussed in the first place? In other words, what's the point? What does the author want me to know? Asking yourself why is a step in the right direction to finding out the point, or main idea.


NEXT TIME YOU read, ask yourself, "What's the point of this?" The answer will be very closely related to the main idea of the text.


Sometimes the subject of a passage and the main idea get confused. Let's talk about the difference. The subject is what the passage is about. For example:

Before a raindrop finds its way to the ground, it has already been on a long journey. Raindrops begin as water molecules that are in the earth's oceans, lakes, streams, and other bodies of water. As the sun heats the water, the molecules are evaporated up into the clouds. When there are a lot of water molecules gathered in the clouds, they get heavy and fall to the earth as raindrops. Some of those raindrops fall into the earth's oceans, lakes, and streams and the process begins all over again.

The subject of the passage is rain. It's about rain. But the main idea is not just what the passage is about; it's what the author says about the subject. So, if the subject is rain, what do you think the main idea would be? Reread the passage and see if you can figure out what is being said about rain.

Now that you've read it again, think about it. The author explains how water molecules evaporate into the air and form rain that falls and then starts the trip up again. So, the main idea would be something like how rain forms or the rain cycle.

The main idea is, quite literally, the central idea of a passage. All the rest of the text is made up of details that support, or tell more about, that main idea.


      subject = what the passage is about
      main idea = what is said about the subject
      detail = information in other sentences that support, or tell more about, the main idea

Let's look at another passage and see if we can distinguish the subject from the main idea.

In a lot of ways, having a digital camera is better than having a camera with film. For one thing, you can take many more pictures with a digital camera than you can with film. The digital camera holds the pictures on a small memory card. And because film takes up more space than the memory card, digital cameras are often smaller and easier to fit in a bag or pocket. In addition, a digital camera can be plugged directly into a computer, allowing the user to upload the pictures right after taking them and passing them on via e-mail. Film must be taken in to be developed, which is not only a slower process, but also ends up costing more money.

What's the subject of the passage? In other words, what's it about? That's easy, it's about cameras. But the main idea is a bit trickier. Again, the main idea is what is being said about the subject. So, what's being said about digital cameras and film cameras? Read the passage again and see if you can figure out what the main idea is.

One way to determine the main idea is to ask yourself, "What's the point?" and "Why does the author want me to know?" Well, the author seems to be expressing a preference for digital cameras over cameras that use film and giving details to explain why digital cameras are better. So, the main idea could be expressed as follows: Digital cameras are better. Of course, there are other ways to say it, but this is the main idea. Everything else in the passage supports one central, or main, idea.


BE CAREFUL. SOMETIMES the subject and main idea are very similar. Just remember that the main idea may include the subject, but will need support from details.


OFTEN THE MAIN idea is stated in the first sentence, so always check that sentence first.

View Full Article
Add your own comment