You learn a new word. You feel good about it. Three days later, it’s gone. Sound familiar?
This isn’t a sign that you’re bad at languages. It’s a sign that you’re reviewing at the wrong time. Spaced repetition fixes this — and it’s backed by over a century of memory research.
The Forgetting Curve
In 1885, German psychologist Hermann Ebbinghaus ran a series of experiments on his own memory. He discovered that newly learned information decays exponentially over time — what he called the forgetting curve.
Without any review, you’ll typically forget:
- 50% within an hour
- 70% within 24 hours
- 90% within a week
These numbers look discouraging. But Ebbinghaus also discovered something hopeful: each time you review information at the right moment, the forgetting curve flattens. The memory becomes more durable. After enough well-timed reviews, the information moves into long-term memory and stays there.
What Is Spaced Repetition?
Spaced repetition is a review strategy based on a simple principle: review just before you forget.
Instead of cramming all your vocabulary study into one session (which feels productive but isn’t), you spread reviews out over increasing intervals:
- Learn a new word
- Review it after 1 day
- Review it after 3 days
- Review it after 7 days
- Review it after 14 days
- Review it after 30 days
- And so on…
Each successful review pushes the next review further into the future. Each failed review pulls it closer. Over time, words you know well barely appear, while words you struggle with keep coming back.
Why It’s So Effective
You Spend Time Where It Matters
Without spaced repetition, you waste time reviewing words you already know. With it, every review session focuses on the words that are at risk of being forgotten. This makes your study time dramatically more efficient.
Difficulty Aids Memory
There’s a counterintuitive finding in memory research called desirable difficulty. Retrieving a memory that’s just starting to fade strengthens it more than retrieving a memory that’s still fresh. Spaced repetition exploits this by timing reviews at the moment of maximum difficulty — right before you’d forget.
This is why spaced repetition feels harder than cramming. And it’s exactly why it works better.
It Scales
A spaced repetition system can manage thousands of words without overwhelming you. You might have 3,000 words in your review system but only see 20-30 per day — the ones that need your attention right now. The rest are safely stored at intervals of weeks or months.
The Problem With Traditional Flashcard Apps
If spaced repetition is so effective, why do so many people abandon their flashcard apps?
The answer is usually one of two problems:
1. Manual Card Creation
Creating flashcards is tedious. You learn a word, switch to your flashcard app, type the word and its translation, maybe add an example sentence, and switch back. This friction adds up. Most people stop creating cards long before they stop learning new words.
The solution is automatic card creation. When your vocabulary system captures words as you encounter them — while reading, during lessons, in conversations — the busywork disappears entirely.
2. Decontextualised Review
A flashcard that says “mesa = table” gives your brain almost nothing to work with. There’s no story, no image, no situation attached to the word. Reviews become a mechanical exercise in pattern matching rather than genuine recall.
The best vocabulary review preserves context. Reviewing a word alongside the sentence where you first encountered it, or the topic you were studying when you learned it, gives your brain the retrieval cues it needs to encode the word deeply.
How to Use Spaced Repetition Effectively
Don’t Create Cards Manually
Use a system that captures vocabulary automatically from your reading and lessons. Your job is to learn — the system’s job is to track what you’ve learned and when to review it.
Keep Sessions Short
Fifteen minutes of daily review is better than an hour once a week. Spaced repetition works best with consistent, brief sessions. Most people find that 20-30 cards per day is sustainable long-term.
Trust the Algorithm
When a word keeps appearing, it means the system has detected that you’re struggling with it. Don’t get frustrated — be grateful. The system is doing its job by focusing your attention where you need it most.
Let It Run in the Background
Spaced repetition shouldn’t be the centrepiece of your language learning. It’s a maintenance system — a way to make sure that the vocabulary you acquire through reading, conversation, and lessons doesn’t slip away. Think of it as insurance for your memory.
The End Result
After a few months of consistent spaced repetition, something magical happens: you stop forgetting. Words that once needed daily review now appear once a month. Your active vocabulary grows steadily because new words stick instead of fading.
You’ll never again have that frustrating experience of re-learning a word for the fifth time. Once it’s in the system, it’s there for good.