Spaced repetition for language learning: how the schedule works

What spaced repetition actually is

Learn a word today and you'll forget most of it within days. That's not a flaw in you, it's the forgetting curve Hermann Ebbinghaus mapped back in 1885: memory of new information drops off fast, then faster. Spaced repetition works with that curve instead of against it. You review a word just as it's about to slip, which flattens the curve a little each time. First you might need it back after a day, then three days, then a week, then a month. The gaps widen as the word gets stronger.

Cram all your reviews into one sitting and you get the opposite: it feels productive and it's mostly gone by Friday. Spread the same reviews out and far more sticks. Psychologists call it the spacing effect, and it's one of the most replicated findings in learning research. A review of 317 experiments (Cepeda and colleagues, 2006) found spaced study beat massed study for lasting recall again and again.

Why it fits language learning in particular

A language is thousands of small things you have to recall on demand: words, genders, verb endings, set phrases. That's exactly the load spaced repetition is built for. But vocabulary drills alone won't get you speaking, so the method matters more than most flashcard apps admit. Two things make the difference for a language:

• Whole sentences, not single words. Reviewing casa on its own teaches you a dictionary entry. Reviewing it inside a sentence you'd actually say teaches you how it behaves, and pulls in grammar and word order for free.
• Audio on every card. You can read a language long before you can follow someone speaking it fast. If your cards are silent, your ear never catches up. Native audio on each sentence trains listening at the same time as memory.

The schedule: from fixed intervals to FSRS

The simplest version is a fixed schedule: review after 1 day, then 3, then 7, and so on. It works, and it's better than nothing. The problem is it treats every card the same, when some words stick on the first try and others fight you for weeks. Older apps used an algorithm called SM-2 to adjust the gaps a bit per card. Newer ones use FSRS, the Free Spaced Repetition Scheduler, an open-source model trained on millions of real reviews that predicts the moment you're about to forget each specific card and schedules it for just before. In practice that means noticeably fewer reviews for the same retention. We wrote up the difference in FSRS versus SM-2 if you want the detail. TangoLango runs FSRS, the same scheduler you can switch on in Anki.

Does it work, and where it doesn't

It works. But it's not magic, and knowing the limits saves you some frustration. Spaced repetition is the best tool there is for getting vocabulary to stay put. It is not, on its own, fluency. The limits worth knowing:

• Recognising a word isn't using it. Cards get you to understand fast. Speaking still needs speaking. Pair your reviews with real conversation.
• Cards you didn't choose don't stick as well. A generic 5,000-word deck feels like a chore because none of it is yours. Words from your own life stick because your brain has a reason to keep them.
• Building the cards is where people quit. The method is proven; the admin around it is what kills the habit. Anything that removes the card-building keeps you going longer.

For the full evidence and an honest look at the objections, see does spaced repetition work for language learning.

How to actually do it

You can do spaced repetition for free. Pick a scheduler (Anki is the free standard), make cards from sentences you meet in real material rather than a random word list, put audio on each one, and review daily. That genuinely works, and if you like building decks it's a great setup.

What we built removes the two steps that make people stop: choosing what to learn and building the cards. In TangoLango you capture the word or message you got stuck on, or just ask the in-app tutor, and it writes the sentence, checks the translation for your dialect, adds native audio, and schedules it with FSRS. You show up for ten minutes; it handles the rest. If you'd rather just compare apps, we line them up on the best spaced repetition app for language learning and, for any subject, a spaced repetition app that builds its own cards. To see real cards, flip through the European Portuguese flashcards. Spaced repetition is the core of how we handle vocabulary. The language learning methods page walks through the rest of the system.

Frequently asked questions