Finding the main idea or theme of a written piece is one of the most important aspects of good reading comprehension. It is, however, easy to confuse the main idea or theme with the subject. Basically, the subject of a piece of writing is what that piece is generally about, plain and simple – the facts and information. However, when you look past the facts and information to the heart of what writers are trying to say, and why they are saying it, that’s the main idea or theme. For example, the subject of this introduction is about distinguishing between a subject and a main idea or theme; the main idea or theme is why it is important to be able to recognise that difference.

The main idea is the point that the writer is trying to help the reader understand, whereas the topic is what the writer is using to get “main ideas across.”