Real understanding shows up when you explain something in plain words to a beginner. Where the explanation gets vague or jargon-filled is exactly where your understanding is thin.
The Feynman technique: explain an idea in plain language as if teaching a beginner — the moment you stumble is the exact gap in your understanding.
Try explaining how interest compounds, or why the sky is blue, to a curious ten-year-old — no jargon allowed. You'll cruise until you hit a sentence you can only fill with borrowed words. That stumble isn't a wording problem; it's the precise spot where you don't actually understand it.
The physicist Richard Feynman was famous for distilling hard ideas into simple, vivid explanations. The learning method named after him turns that into a tool: pick a concept, explain it plainly as if teaching someone new, notice where you get stuck or reach for jargon, then return to the source and fill that gap. Repeat until the whole thing flows in simple language.
Don't measure understanding by whether you've read or highlighted something — measure it by whether you can explain it cleanly to a beginner. Teach it out loud or on paper. The gaps will announce themselves, and closing them is what turns familiarity into real knowledge.
It's a built-in honesty test for learning — it exposes the difference between recognizing an idea and actually understanding it.
Confused with "explain it simply." The power is in the failure: trying to teach something in plain words exposes exactly where your understanding is fake or borrowed. The point isn't the simple explanation — it's using the attempt to find and fix the gaps you didn't know you had.
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