Spaced repetition makes you review a word right before you forget it. Here is how it works, why it doubles retention, and how to use it without an app.
Spaced repetition is the single most-tested technique in memory research. If you ever wondered why some words stick on the first try and others vanish in a week, the answer is almost always timing.
Instead of reviewing every word every day, spaced repetition shows you a word at increasing intervals — 1 day, 3 days, 7 days, 16 days — and only resets when you forget. The harder a card feels, the sooner it comes back.
This idea goes back to Hermann Ebbinghaus in 1885. He plotted how memory decays over time and noticed that a brief review right before you forget flattens the curve. Modern apps (Anki, SuperMemo, Tilingu) automate the math behind it.
Three things happen when you re-encounter a word at the right time:
You don't need fancy software to start, but you do need consistency.
Tilingu uses the SM-2 algorithm (the same one Anki popularized) and handles the scheduling for you. Add a word, the system picks when you see it next. After two weeks you'll notice you're recalling words you only saw twice.