How we make these materials

Where the material comes from

The words, explanations, dialogues and reading texts are the very same ones as in the courses. These pages were not written separately “for search engines”: what you read here will meet you word for word in a lesson.

The topics and their order also come from the course. The page only puts it all on shelves and ties it together with links.

Why everyone can hear the sound

The sound is prepared in advance and stored right on the site. That is why it works for everyone the same way: nothing to install, nothing depends on your phone.

Many sites do it differently: they ask your phone to read the word aloud. With Armenian, Georgian, Kazakh and Maldivian that almost always ends in silence — hardly any phone carries those voices.

And one more rule: no recording, no button. That way you can see at once what you can listen to and what you cannot.

Where the numbers come from

Next to every number on the site there is a link to the study it comes from. And a note: some things scientists have checked many times and are sure of, others are so far only suggested. It says which is which — you can check yourself.

• Studying a little every day gets more into your head than spending the same total time in one sitting.checked many times
  Donovan & Radosevich, 1999, Journal of Applied Psychology 84(5) · 63 studies compared, difference d = 0.46 — a sizeable figure for a learning effect.
• This holds not only in experiments but in ordinary classrooms, with real students.checked many times
  Mawson & Kang, 2025, Behavioral Sciences 15(6):771 · 22 studies, d = 0.54 (confidence interval 0.31–0.77). The authors warn that individual studies disagree widely.
• The longer you want to keep a word, the rarer its repetitions should be. To hold it for a week, review every day; to hold it for a year, about once a month.checked many times
  Cepeda et al., 2008, Psychological Science 19(11) · Over 1,350 participants, tested after delays of up to a year. The best gap is about 20% of the target interval on a horizon of weeks, and 5–10% on a horizon of a year.
• This has been tested on foreign words too. The difference shows up most when you test yourself a few days later rather than straight away.checked many times
  Kim & Webb, 2022, Language Learning 72(2) · 48 experiments, 3,411 participants, 98 comparisons.
• Recalling beats re-reading. Covering the translation and trying to remember it does more than reading it ten more times.checked many times
  Adesope, Trevisan & Sundararajan, 2017, Review of Educational Research 87(3) · 188 experiments, 272 comparisons. g = 0.61; against plain re-reading 0.51, against passive review 0.93.
• It is better to test yourself the next day than at the end of the same session. That is why a word comes back to you tomorrow.checked many times
  Adesope, Trevisan & Sundararajan, 2017, Review of Educational Research 87(3) · g = 0.82 when tested a day or two later, against 0.56 on the same day.

The full list is on the Sources page.

What you will not see here

• Promises to learn a language in a month. In a month, twenty minutes a day really does get you reading and a hundred words.
• Invented reviews and “only three spots left” counters.
• Per-sound advice like “soften the aspiration”: no working tool exists for that yet, and made-up advice that a person follows is harmful.
• Invented experts with certificates. The materials are signed by the project, and everything checkable carries a link to the primary source.

Next

• SourcesThe research we build on
• About the projectWho does this and why