Why You Forget Vocabulary Words (And How to Actually Remember Them)
Within 20 minutes of learning something new, you forget about 40% of it. Within one day, nearly 70% is gone. This isn’t a personal failing—it’s the forgetting curve, discovered by Hermann Ebbinghaus in the 1880s and confirmed by memory research ever since.
Your brain isn’t broken. It’s doing exactly what it evolved to do: filter out information that doesn’t seem important. The problem is that your brain can’t tell the difference between “unimportant street sign” and “vocabulary word I actually need.” New words get thrown out with the noise unless you deliberately show your brain they matter.
Understanding how this filtering works—and how to work with it instead of against it—changes everything about vocabulary retention.
Why Your Brain Forgets (On Purpose)
Your brain filters out information it considers unimportant. This makes sense—you don’t need to remember every face you passed on the street or every sign you glanced at. The problem is that your brain can’t tell the difference between “unimportant street sign” and “vocabulary word I actually need.”
Think about a word like “cookie” in Japanese. When you hear it, your brain doesn’t just see a label—it activates everything you know about cookies. The smell of baking. The texture. That time you burned your tongue because you couldn’t wait. Your brain has built a massive web of sights, sounds, and personal history around that word.
A new English word like “puppy” starts with none of that. It’s essentially naked—just a strange sound with no connections. Your brain’s natural filter treats it as irrelevant noise and throws it out to prevent information overload. This is why foreign words feel so forgettable at first. They lack the rich web of meaning that makes native words effortless to recall.
To make a word stick, you have to build those connections deliberately. The more you tie a new word to images, experiences, and personal memories, the more your brain treats it like a word worth keeping.
This is also why reading over word lists rarely works. Reading is recognition—your brain sees the word, thinks “yes, I know that,” and moves on. But recognition isn’t the same as recall. You can recognize a word instantly on a page while having no ability to produce it when you need to speak.
Method 1: Test Yourself (Active Recall)
The single most effective thing you can do is stop reviewing and start testing.
Here’s how it works in practice. After studying a set of vocabulary words, put the textbook away. Take a blank piece of paper and try to write down everything you remember. Don’t peek. Just sit there and pull words out of your memory, one by one.
This feels harder than reviewing, and that’s exactly the point. The effort of retrieval is what creates lasting memory. Research consistently shows that testing yourself once is more effective than studying the same material multiple times. The struggle to remember is doing the actual work.
When I tried this with that same student, we started with something simple: I had him read Green Eggs and Ham, then gave him a blank sheet of paper and asked him to write down every word he could remember from the story. We did the same thing later with vocabulary from a dialog in his textbook. The difference was immediate—not because anything magical happened, but because he was finally practicing the right skill: producing words from memory rather than just recognizing them on a page.
Method 2: Connect Words to Real Things
A vocabulary word floating alone in your head is fragile. “Puppy” connected only to “子犬” can slip away easily because it’s just two sounds linked together, hanging in empty space.
But “puppy” connected to an image of your neighbor’s clumsy golden retriever, the one that knocked over your bike last week—that sticks. Now the word has weight. It’s attached to something real in your experience, not just an abstract translation.
When learning new words, take a moment to picture something specific. Not a generic mental image, but something from your actual life. Where have you seen this thing? What did it look like, sound like, feel like? The more vivid and personal the connection, the harder the word becomes to forget.
This works because memory isn’t stored in isolation. Words are patterns of connections in your brain—the more connections, the more paths back to that word when you need it.
Method 3: Time Your Reviews (Spaced Repetition)
There’s an optimal moment to review a word: right before you forget it.
If you review too early, the practice is too easy—your brain doesn’t work hard enough to strengthen the memory. If you review too late, you’ve already forgotten and have to start over.
The sweet spot is that frustrating moment when the word is on the tip of your tongue. You know you know it. You’re reaching for it. This struggle, followed by successful recall, locks the word in far more effectively than easy recognition ever could.
The pattern that works: review after a few hours, then a day, then a few days, then a week. Each successful recall extends the interval. You’re not memorizing through repetition—you’re building retrieval strength through strategically timed challenge.
This is why cramming before a test feels productive but leaves nothing behind. You might pass the test, but a month later those words are gone. Spaced review, spread over time, creates memory that lasts.
What This Means for Your Studying
The student who learns the word “puppy” on Saturday but forgets it by Monday isn’t failing. He’s doing what brains naturally do. The fix isn’t more willpower or longer study sessions—it’s changing how he interacts with vocabulary.
Test yourself instead of reviewing. Connect words to real experiences. Space your practice over days, not hours.
None of this requires special tools or apps (though they can help). A blank piece of paper and honest effort are enough. The key is understanding that memory isn’t passive—it’s built through active retrieval, and struggle is the point, not the problem.
If vocabulary has always felt like water slipping through your fingers, this approach might finally make things stick.
Ready to learn study methods that actually work?
I teach techniques like these as part of regular lessons—helping students build skills that last beyond the next test.