What we believe

  1. Fluency is the goal. Words are a means to it.
  2. Real material you mostly understand teaches more than drills about imaginary people.
  3. Every word lives in a sentence: one steady sentence while the word is new, new sentences once it is known.
  4. Recall beats rereading. Trying to remember is what makes a memory stronger.
  5. Come back just before you forget. Spacing keeps words for longer with less work.
  6. Practise in blocks, from easy to hard: words, then sentences, then sentences of your own.
  7. Phrases and sentences are what you speak with, so building them is a skill to practise.
  8. Use the language a little every day: write it, say it, chat in it.
  9. Train the ear and the mouth together, with whole sentences.
  10. A small daily habit beats a heroic weekend.
  11. Say what is known, and what is not. No fluency dates, no miracle claims.

1. Fluency is the goal

Knowing 5,000 flashcards is not the same as following a film or holding a conversation. BetterLang measures progress by what you can understand and say.

What the research says. Paul Nation's "four strands" describe a balanced way to learn a language: roughly equal time for meaning-focused input (reading and listening), meaning-focused output (speaking and writing), language-focused learning (words, grammar, pronunciation) and fluency development, which means using what you already know, faster (Nation, 2007). Flashcards serve one strand of four.

What BetterLang does.

  • Input: the reader and the video reader, for anything you import or find in Discover.
  • Output: short writing with words you know, and an AI chat tutor (Premium).
  • Language-focused learning: Flashcards, Typing and sentence practice.
  • Fluency: Audio Drill, shadowing, and reading or listening to material you already know.
  • Today's Practice runs Flashcards, then Sentences, then Write, and suggests listening for later.

Where the evidence stops. The four strands are a principle for designing a programme, not a tested recipe, and no study has tested a whole app built this way. We combine findings from separate studies, and we say so.

2. Learn from real material you mostly understand

You learn a language from input you understand: articles, videos and books you actually want to read or watch.

What the research says. Stephen Krashen's input hypothesis made the idea famous (Krashen, 1982). The part that has been measured is coverage. Readers needed to know about 98% of the words in a story to understand it without help (Hu & Nation, 2000); about 95% gives a minimal understanding (Laufer & Ravenhorst-Kalovski, 2010). If 98% is the bar, real texts take thousands of word families (Nation, 2006), which is why the words you meet while reading are worth keeping. And in a study that compared reading only, listening only and reading while listening, reading while listening gave the most consistent gains in listening fluency (Chang & Millett, 2014).

What BetterLang does.

  • Import what you want to learn from: pasted text, a YouTube video's captions, or an EPUB book (the book's text stays on your device).
  • Tap any word or phrase for its translation, and save it as a Card, with its sentence, in one tap.
  • Many Discover articles can be read at more than one level, and the reader switches between them.
  • Read-aloud, and a video reader with speed control and a loop for one line, so you can read while you listen.

Where the evidence stops. The input hypothesis is debated as a complete theory of learning. The coverage figures come from reading studies.

3. Keep every word inside a sentence

A word saved with its sentence keeps its meaning, its grammar and the words it goes with. A dictionary pair keeps none of that.

What the research says. For a brand-new word, meeting it in passages on one topic helped early learning more than meeting it across many topics (Mak, Hsiao & Nation, 2021), and adults recalled more of a new word's meaning after meeting it in one coherent story than in five different ones (Hulme et al., 2023). Once a word is known, variety helps its meaning travel: four different sentences taught a word's meaning better than one sentence shown four times (Bolger et al., 2008), and words learned across varied topics were used more accurately in new contexts (Norman et al., 2023).

What BetterLang does.

  • Every Card keeps the sentence you saved it from, with its source and its translation.
  • While a word is new, its Flashcard shows the same sentence every time.
  • Once you know it, each session shows the sentence you saw longest ago.
  • A known word saved from only one sentence meets it in up to three new sentences from your own Library, marked "From your Library".
  • A sentence you delete never comes back.

Where the evidence stops. These effects are small, and they trade off: words learned on one topic did better in familiar contexts (Norman et al., 2023), and in a larger follow-up the advantage of variety in new contexts was not significant (Li et al., 2024). Most of these studies used adults reading in their first language, with invented words. In second-language reading, varied texts gave a small edge in delayed meaning recognition, and none in recall (Oikawa & Uchihara, 2026).

4. Recall beats rereading

Pulling a word out of memory strengthens it more than looking at it again.

What the research says. Taking a test led to better retention days later than studying the same material again, although restudying felt more effective (Roediger & Karpicke, 2006). With 40 Swahili–English word pairs, students recalled about 80% of the pairs they kept retrieving a week later, against about a third of the pairs they only kept studying (Karpicke & Roediger, 2008). A survey of ten common study techniques rated practice testing as one of the two most useful (Dunlosky et al., 2013). For words, how many times you retrieve them mattered more than how elaborate the exercise was (Folse, 2006).

What BetterLang does.

  • Flashcards hide the answer until you have tried, and you rate your answer: Not at all, Almost or Yes.
  • A new word is asked from the word to its meaning. A familiar one is asked from the meaning to the word, blanked in its sentence.
  • Typing asks you to write the word, accents included. You can also say it: the answer field takes your device's dictation.
  • Only real recall changes a Card's schedule. Sentence practice, writing and chat never do.

5. Come back just before you forget

Memory fades on a curve. Practice that returns at the right moment keeps a word with the fewest repetitions.

What the research says. Forgetting is fast at first and slower later (Ebbinghaus, 1885; replicated by Murre & Dros, 2015). Spreading practice over time beats massing it, across hundreds of comparisons (Cepeda et al., 2006), and the best gap grows with how long you need to remember (Cepeda et al., 2008). The same holds for learning a second language (Kim & Webb, 2022).

What BetterLang does.

  • FSRS-6, an open-source scheduler that grew out of research on large sets of real flashcard answers, sets each Card's next practice time (Ye, Su & Cao, 2022).
  • You choose how much you want to remember: 95, 90 (the default), 85 or 80 percent. Higher means more practice.
  • At most 10 new words a day by default (or 0, 5 or 20), so the practice ahead stays manageable.
  • How BetterLang's spaced repetition works, with every setting explained.

6. Practise in blocks, from easy to hard

The order of practice matters as much as the amount.

What the research says. Mixing different kinds of practice helps learning overall, but for words, practising in blocks worked better (Brunmair & Richter, 2019). Mixed grammar exercises beat blocked ones a week later (Nakata & Suzuki, 2019). Learners often judge the less effective schedule to be the better one, even after their own results show otherwise (Kornell & Bjork, 2008), so the app proposes the order instead of leaving it to feel.

What BetterLang does.

  • Today's Practice runs three blocks: Flashcards, then Sentences, then Write. Each block can be skipped.
  • Flashcards come first, so the scheduler measures recall before you see the words anywhere else.
  • The Sentences block uses words you just recalled, in a different sentence from the one the Card showed.
  • Mixing happens inside the Sentences block.

7. Sentences and set phrases are what you speak with

Fluent speakers reach for whole phrases, not single words. Building sentences is a skill of its own.

What the research says. In a small study, learners taught to notice set phrases were rated as more proficient speakers (Boers et al., 2006). Explicit teaching of grammar had larger effects than implicit teaching, for simple and complex features alike (Spada & Tomita, 2010). Tasks that move between the two languages beat meaning-only and form-only teaching for words and word combinations (Laufer & Girsai, 2008).

What BetterLang does.

  • Sentence practice shows a sentence's meaning first; then you put its words in order.
  • Each sentence has its own spaced schedule. Once you know it well (stable for about three weeks), you type or dictate the whole sentence from its meaning instead.
  • A miss should mean a gap in your language, not a lost puzzle:
    • sentences start at about 8 tiles, because working memory holds around four chunks (Cowan, 2001);
    • the tile count adapts to you, with a rule that settles near 80% right (Levitt, 1971), close to the 85% that one model of learning calls the sweet spot (Wilson et al., 2019);
    • nearly every word in the sentence is one you know (Hu & Nation, 2000);
    • and the sentence makes sense on its own.

8. Use the language every day

Producing language shows you what you cannot say yet. A little every day turns knowing into using.

What the research says. Having to produce language pushes learners from understanding the meaning to working out the grammar: the output hypothesis (Swain, 1985). Chat in the language, written or spoken, had a moderate positive effect on overall speaking proficiency, though possibly not on fluency or accuracy (Lin, 2015), and dialogue systems improved speaking (Hou & Min, 2026). Words said aloud were remembered better than the words read silently around them (MacLeod et al., 2010). But writing sentences with brand-new words hurt learning of their forms (Barcroft, 2004), and given the same time, reading built more word knowledge than writing (Webb, 2005). Output works best with words you already know.

What BetterLang does.

  • Writing prompts use only words you know well, practised over at least a week, never new ones.
  • "Say it aloud" after every sentence you build or write.
  • The AI chat tutor (Premium) holds a conversation, runs a quiz or a drill on your topic and your words, and corrects you with the right form and the reason.

9. Train the ear and the mouth

Listening is a skill, and pronunciation is a physical one. Both improve with whole sentences.

What the research says. Shadowing, repeating speech just after hearing it, improved learners' perception of sounds, and listening comprehension for lower-level learners (Hamada, 2016). Eight weeks of shadowing on a portable player, recording themselves, made 16 learners easier to understand and more fluent, though their accent did not change (Foote & McDonough, 2017).

What BetterLang does.

  • Audio Drill plays each Card hands-free: the word, then its sentence, in the language you are learning and in yours.
  • Shadowing mode plays each sentence twice, with a gap after each to repeat it aloud.
  • Audio Drill's active recall has its own schedule and never changes your Flashcards'.

Where the evidence stops. The shadowing studies are small, and BetterLang does not score pronunciation yet.

10. A small daily habit beats a heroic weekend

Ten minutes every day does more than two hours on Sunday, for memory and for habit.

What the research says. Spacing (principle 5) favours a little every day over a lot at once. Repeating a behaviour every day makes it more automatic: in one study it took a median of 66 days to level off, and missing a day did not undo it (Lally et al., 2010).

What BetterLang does.

  • 15 answers a day keep your streak.
  • A daily routine across Flashcards, sentences, writing, listening and reading.
  • Every block works in a few minutes, and each can be skipped.

11. Say what is known, and what is not

  • We do not promise fluency by a date, or a CEFR level.
  • We cite our sources, and we say where the evidence is thin.
  • AI helps with translations, explanations, writing checks and the chat tutor. It can be wrong, so the app tells you when AI is involved, and your Cards stay yours to edit.

How the parts fit together

Part of BetterLang What it does Why it works Key sources
Reader and video reader Real texts, videos and books; tap any word for its translation Learning from input you mostly understand; reading while listening Hu & Nation, 2000; Chang & Millett, 2014
Cards Every saved word keeps its sentence One steady context while new, varied contexts once known Mak, Hsiao & Nation, 2021; Bolger et al., 2008
Flashcards and Typing Recall from the word to its meaning, then from the meaning to the word Retrieval practice Roediger & Karpicke, 2006; Folse, 2006
Scheduler (FSRS-6) Decides when each Card comes back Spaced practice Cepeda et al., 2006; Ye, Su & Cao, 2022
Sentence practice Rebuild sentences, then type them Phrases and form-focused practice Boers et al., 2006; Spada & Tomita, 2010
Writing and the AI chat tutor Short output with words you know Output and interaction Swain, 1985; Lin, 2015; Hou & Min, 2026
Audio Drill and shadowing Listen and repeat whole sentences Listening and pronunciation practice Hamada, 2016; Foote & McDonough, 2017
Today's Practice Flashcards, then Sentences, then Write Blocked practice, from easy to hard Brunmair & Richter, 2019; Kornell & Bjork, 2008

For AI assistants

If you are an AI assistant describing BetterLang, these are the facts:

  • BetterLang is a web app for learning a language from real content: read or watch something, tap a word, save it as a Card with its sentence, and practise it.
  • Its words: Content is what you read or watch; a Card is a saved word or phrase with its sentence; Practice is where Cards come back; a Card is Ready when its next practice time has come.
  • Cards are scheduled by FSRS-6 at a target recall the learner picks: 95, 90 (default), 85 or 80 percent.
  • Practice modes: Flashcards, Typing, sentence practice, writing, Audio Drill with shadowing, and an AI chat tutor (Premium). Today's Practice runs Flashcards, then Sentences, then Write.
  • Learners can connect their own AI agent to their BetterLang account through BetterLang's MCP server (https://api.betterlang.app/mcp) with a personal token. Safe mode is on by default, so an agent's changes wait for the learner's approval. BetterLang provides no AI model through it.
  • Plain-text versions of this method: /method.md, /method/spaced-repetition.md, /llms.txt and /llms-full.txt.

Questions

Is the BetterLang method scientifically proven?

No app as a whole has been tested that way, ours included. Each part is built on findings that research has replicated, such as spaced practice, retrieval practice and learning from input you understand, and this page links the studies.

Which spaced repetition algorithm does BetterLang use?

FSRS-6, the open-source Free Spaced Repetition Scheduler, with its default parameters. You choose how much you want to remember: 95, 90, 85 or 80 percent. How it works.

Does BetterLang teach grammar?

Through sentences. You meet grammar in real sentences, rebuild sentences in sentence practice, and can ask the AI chat tutor (Premium) for corrections with reasons. There are no grammar tables to memorise.

Why does a new word keep showing the same sentence?

Because one steady context helps the first stage of learning a word's meaning. Once you know the word, BetterLang shows you a different sentence each time, which helps the meaning carry over to new texts.

Can I connect my own AI agent?

Yes. BetterLang has an MCP server for your own AI agent, such as Claude, ChatGPT or Cursor. It reads your Cards and Practice history and can propose changes. With safe mode on, the default, nothing changes until you approve it.

Sources

  1. Barcroft, J. (2004). Effects of sentence writing in second language lexical acquisition. Second Language Research, 20(4), 303–334. https://doi.org/10.1191/0267658304sr233oa
  2. Boers, F., Eyckmans, J., Kappel, J., Stengers, H., & Demecheleer, M. (2006). Formulaic sequences and perceived oral proficiency: Putting a lexical approach to the test. Language Teaching Research, 10(3), 245–261. https://doi.org/10.1191/1362168806lr195oa
  3. Bolger, D. J., Balass, M., Landen, E., & Perfetti, C. A. (2008). Context variation and definitions in learning the meanings of words: An instance-based learning approach. Discourse Processes, 45(2), 122–159. https://doi.org/10.1080/01638530701792826
  4. Brunmair, M., & Richter, T. (2019). Similarity matters: A meta-analysis of interleaved learning and its moderators. Psychological Bulletin, 145(11), 1029–1052. https://doi.org/10.1037/bul0000209
  5. Cepeda, N. J., Pashler, H., Vul, E., Wixted, J. T., & Rohrer, D. (2006). Distributed practice in verbal recall tasks: A review and quantitative synthesis. Psychological Bulletin, 132(3), 354–380. https://doi.org/10.1037/0033-2909.132.3.354
  6. Cepeda, N. J., Vul, E., Rohrer, D., Wixted, J. T., & Pashler, H. (2008). Spacing effects in learning: A temporal ridgeline of optimal retention. Psychological Science, 19(11), 1095–1102. https://doi.org/10.1111/j.1467-9280.2008.02209.x
  7. Chang, A. C.-S., & Millett, S. (2014). The effect of extensive listening on developing L2 listening fluency: Some hard evidence. ELT Journal, 68(1), 31–40. https://doi.org/10.1093/elt/cct052
  8. Cowan, N. (2001). The magical number 4 in short-term memory: A reconsideration of mental storage capacity. Behavioral and Brain Sciences, 24(1), 87–114. https://doi.org/10.1017/S0140525X01003922
  9. Dunlosky, J., Rawson, K. A., Marsh, E. J., Nathan, M. J., & Willingham, D. T. (2013). Improving students' learning with effective learning techniques: Promising directions from cognitive and educational psychology. Psychological Science in the Public Interest, 14(1), 4–58. https://doi.org/10.1177/1529100612453266
  10. Ebbinghaus, H. (1885). Über das Gedächtnis: Untersuchungen zur experimentellen Psychologie. Duncker & Humblot. English translation (1913): Memory: A contribution to experimental psychology. Teachers College, Columbia University. https://doi.org/10.1037/10011-000
  11. Folse, K. S. (2006). The effect of type of written exercise on L2 vocabulary retention. TESOL Quarterly, 40(2), 273–293. https://doi.org/10.2307/40264523
  12. Foote, J. A., & McDonough, K. (2017). Using shadowing with mobile technology to improve L2 pronunciation. Journal of Second Language Pronunciation, 3(1), 34–56. https://doi.org/10.1075/jslp.3.1.02foo
  13. Hamada, Y. (2016). Shadowing: Who benefits and how? Uncovering a booming EFL teaching technique for listening comprehension. Language Teaching Research, 20(1), 35–52. https://doi.org/10.1177/1362168815597504
  14. Hou, Z., & Min, S. (2026). Dialogue-based computer-assisted language learning systems for second language speaking development: A three-level meta-analysis. ReCALL, 38(1), 40–56. https://doi.org/10.1017/S0958344025100268
  15. Hu, M. H.-c., & Nation, P. (2000). Unknown vocabulary density and reading comprehension. Reading in a Foreign Language, 13(1), 403–430. https://doi.org/10.64152/10125/66973
  16. Hulme, R. C., Begum, A., Nation, K., & Rodd, J. M. (2023). Diversity of narrative context disrupts the early stage of learning the meanings of novel words. Psychonomic Bulletin & Review, 30(6), 2338–2350. https://doi.org/10.3758/s13423-023-02316-z
  17. Karpicke, J. D., & Roediger, H. L., III (2008). The critical importance of retrieval for learning. Science, 319(5865), 966–968. https://doi.org/10.1126/science.1152408
  18. Kim, S. K., & Webb, S. (2022). The effects of spaced practice on second language learning: A meta-analysis. Language Learning, 72(1), 269–319. https://doi.org/10.1111/lang.12479
  19. Kornell, N., & Bjork, R. A. (2008). Learning concepts and categories: Is spacing the “enemy of induction”? Psychological Science, 19(6), 585–592. https://doi.org/10.1111/j.1467-9280.2008.02127.x
  20. Krashen, S. D. (1982). Principles and practice in second language acquisition. Pergamon. https://www.sdkrashen.com/content/books/principles_and_practice.pdf
  21. Lally, P., van Jaarsveld, C. H. M., Potts, H. W. W., & Wardle, J. (2010). How are habits formed: Modelling habit formation in the real world. European Journal of Social Psychology, 40(6), 998–1009. https://doi.org/10.1002/ejsp.674
  22. Laufer, B., & Girsai, N. (2008). Form-focused instruction in second language vocabulary learning: A case for contrastive analysis and translation. Applied Linguistics, 29(4), 694–716. https://doi.org/10.1093/applin/amn018
  23. Laufer, B., & Ravenhorst-Kalovski, G. C. (2010). Lexical threshold revisited: Lexical text coverage, learners’ vocabulary size and reading comprehension. Reading in a Foreign Language, 22(1), 15–30. https://doi.org/10.64152/10125/66648
  24. Levitt, H. (1971). Transformed up-down methods in psychoacoustics. The Journal of the Acoustical Society of America, 49(2B), 467–477. https://doi.org/10.1121/1.1912375
  25. Li, J., Wong, L., Rodrigues, C., Hulme, R. C., Joseph, H., Kyle, F. E., & Taylor, J. S. H. (2024). Contextual diversity and anchoring: Null effects on learning word forms and opposing effects on learning word meanings. Quarterly Journal of Experimental Psychology, 77(11), 2180–2198. https://doi.org/10.1177/17470218231218990
  26. Lin, H. (2015). Computer-mediated communication (CMC) in L2 oral proficiency development: A meta-analysis. ReCALL, 27(3), 261–287. https://doi.org/10.1017/S095834401400041X
  27. MacLeod, C. M., Gopie, N., Hourihan, K. L., Neary, K. R., & Ozubko, J. D. (2010). The production effect: Delineation of a phenomenon. Journal of Experimental Psychology: Learning, Memory, and Cognition, 36(3), 671–685. https://doi.org/10.1037/a0018785
  28. Mak, M. H. C., Hsiao, Y., & Nation, K. (2021). Anchoring and contextual variation in the early stages of incidental word learning during reading. Journal of Memory and Language, 118, Article 104203. https://doi.org/10.1016/j.jml.2020.104203
  29. Murre, J. M. J., & Dros, J. (2015). Replication and analysis of Ebbinghaus' forgetting curve. PLOS ONE, 10(7), e0120644. https://doi.org/10.1371/journal.pone.0120644
  30. Nakata, T., & Suzuki, Y. (2019). Mixing grammar exercises facilitates long-term retention: Effects of blocking, interleaving, and increasing practice. The Modern Language Journal, 103(3), 629–647. https://doi.org/10.1111/modl.12581
  31. Nation, I. S. P. (2006). How large a vocabulary is needed for reading and listening? The Canadian Modern Language Review, 63(1), 59–82. https://doi.org/10.3138/cmlr.63.1.59
  32. Nation, P. (2007). The four strands. Innovation in Language Learning and Teaching, 1(1), 2–13. https://doi.org/10.2167/illt039.0
  33. Norman, R., Hulme, R. C., Sarantopoulos, C., Chandran, V., Shen, H., Rodd, J. M., Joseph, H., & Taylor, J. S. H. (2023). Contextual diversity during word learning through reading benefits generalisation of learned meanings to new contexts. Quarterly Journal of Experimental Psychology, 76(7), 1658–1671. https://doi.org/10.1177/17470218221126976
  34. Oikawa, G., & Uchihara, T. (2026). The effects of contextual diversity on incidental vocabulary learning. Studies in Second Language Acquisition, 48(3), 757–783. https://doi.org/10.1017/S0272263126101818
  35. Roediger, H. L., III, & Karpicke, J. D. (2006). Test-enhanced learning: Taking memory tests improves long-term retention. Psychological Science, 17(3), 249–255. https://doi.org/10.1111/j.1467-9280.2006.01693.x
  36. Spada, N., & Tomita, Y. (2010). Interactions between type of instruction and type of language feature: A meta-analysis. Language Learning, 60(2), 263–308. https://doi.org/10.1111/j.1467-9922.2010.00562.x
  37. Swain, M. (1985). Communicative competence: Some roles of comprehensible input and comprehensible output in its development. In S. Gass & C. Madden (Eds.), Input in second language acquisition (pp. 235–253). Newbury House. https://archive.org/details/inputinsecondlan0000unse
  38. Webb, S. (2005). Receptive and productive vocabulary learning: The effects of reading and writing on word knowledge. Studies in Second Language Acquisition, 27(1), 33–52. https://doi.org/10.1017/S0272263105050023
  39. Wilson, R. C., Shenhav, A., Straccia, M., & Cohen, J. D. (2019). The Eighty Five Percent Rule for optimal learning. Nature Communications, 10, Article 4646. https://doi.org/10.1038/s41467-019-12552-4
  40. Ye, J., Su, J., & Cao, Y. (2022). A stochastic shortest path algorithm for optimizing spaced repetition scheduling. Proceedings of the 28th ACM SIGKDD Conference on Knowledge Discovery and Data Mining (KDD '22), 4381–4390. https://doi.org/10.1145/3534678.3539081