The Feynman Technique: check whether you really understand

You can know a definition by heart and still not understand it. This technique, named after physicist Richard Feynman, who was famous for explaining hard things in plain language, helps you quickly tell the two apart.

Step 1: Pick one concept

Write it at the top of a blank page. Just one, and a specific one: “derivative,” “photosynthesis,” or “demand” - not “all of calculus.”

Step 2: Explain it as simply as you can

Write as if someone outside your class or major were reading it. No jargon, and no copying the definition from the textbook. If you have to use a difficult word, explain that word too.

Step 3: Find the gaps

The spots where you get stuck, skip ahead with “and then it somehow works out,” or fall back on the textbook wording are exactly what you don’t understand yet. Go back to your materials for those parts only - then write the explanation again from scratch.

Step 4: Simplify and add an example

Shorten your sentences, add an analogy and one concrete example. If you can explain the concept with an example that wasn’t in your notes, that’s a good sign you really understand it.

Example: the derivative

First version: “A derivative is the limit of the difference quotient.” Correct, but it doesn’t explain anything.

After a few rewrites: “A derivative tells you how fast a function is changing at a given point. Think of a car’s speedometer: distance is a function of time, and your speed at any moment is its derivative. On a graph, it’s the slope of the tangent line - the steeper it is, the faster the change.”

The second explanation shows that you know why the definition exists. If you want to work through this topic step by step, check out the Derivatives from scratch course.