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Science-Backed Learning

Learn Vocabulary Faster with Spaced Repetition

Stop cramming, start remembering. penguen.io uses a scientifically-proven spaced repetition algorithm to show you each word at the perfect moment — just before you forget it. Build permanent vocabulary with less study time.

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The Problem: You Forget 80% Within a Week

In 1885, psychologist Hermann Ebbinghaus discovered the "forgetting curve" — a mathematical model showing how quickly we lose newly learned information. Without review, you forget roughly 50% of new information within an hour, and up to 80% within a week.

This is why cramming vocabulary lists the night before an exam doesn't work. You might pass the test, but the words vanish from memory within days. Traditional flashcard apps don't solve this — they show you every card equally, wasting time on words you already know.

Without Spaced Repetition
After 1 hour
50%
After 1 day
30%
After 1 week
20%
After 1 month
10%
% of vocabulary retained

The Solution: Review at the Right Moment

Spaced repetition flips the forgetting curve on its head. Instead of reviewing everything equally, the algorithm identifies the optimal moment to show you each word — right before you're about to forget it. Each successful review extends the interval.

A new word might be reviewed after 1 day, then 3 days, then 1 week, then 2 weeks, then 1 month. Words you struggle with are shown more frequently. Words you know well fade into the background. The result: you study less but remember more.

With Spaced Repetition on penguen.io
After 1 hour
95%
After 1 day
90%
After 1 week
85%
After 1 month
80%
% of vocabulary retained

How penguen.io Makes Spaced Repetition Easy

psychology

Smart Scheduling

Our algorithm adapts to your performance. Know a word well? You won't see it for weeks. Struggling? It comes back tomorrow.

speed

Difficulty Rating

After each card, rate how well you knew it. The algorithm adjusts the next review interval in real-time based on your feedback.

trending_up

Progress Tracking

See your retention rate, study streaks, and mastered word count. Watch your vocabulary grow day by day with clear visual progress.

More Than Just Flashcards

Spaced repetition powers all six practice modes — not just flashcards.

style

Flashcards

quiz

Multiple Choice

edit

Fill in the Blanks

grid_view

Matching

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Dictation

headphones

Listen & Choose

Spaced Repetition FAQ

What is spaced repetition? expand_more
Spaced repetition is a learning technique where you review information at increasing intervals. Instead of cramming, you study a word right before you're about to forget it — building permanent long-term memory with minimal study time.
How is this different from regular flashcards? expand_more
Regular flashcards show every card equally. Spaced repetition tracks which words you know and which you struggle with, scheduling reviews accordingly. You spend more time on hard words and less on easy ones.
How long until I see results? expand_more
Most learners notice improved retention within the first week. After 2-3 weeks of consistent practice, you'll find you're remembering words you previously kept forgetting. The effect compounds over time.
Is penguen.io better than Anki? expand_more
penguen.io is designed to be simpler and more accessible. While Anki offers deep customization, penguen.io provides a modern, ready-to-use experience with curated collections, multiple practice modes, and AI pronunciation — no complex setup required.

Start Learning with Spaced Repetition

Join thousands of learners who study smarter, not harder. Free to start — no credit card needed.

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