Kotoba

Kotoba is a free, offline-first language-learning Android app. Pick the language you speak (12 supported) and the language you want to learn (also 12), and the entire curriculum — vocabulary, example sentences, grammar patterns and roleplay conversations — is taught with meanings and explanations in your own language. Japanese and English are hand-authored; the other tracks are built on the fly from the English course through bundled offline gloss tables, so no track ever falls back to a language you don't read.

Built on well-established language-learning research:

Spaced Repetition (SM-2) — every word gets its own schedule (10 min → 1 day → 6 days → …). Wrong answers return quickly, right answers stretch out. This "forgetting curve" timing is the highest-leverage technique for long-term retention. Picture association over translation — every word is taught with an emoji and an image-first prompt, so learners map meaning directly to sound, the way native speakers and children do, instead of translating through a third language. Chunking / sentence patterns — learners study whole high-frequency sentences ("I like ~", "please ~") rather than isolated words, matching how fluency is actually built. Kana before kanji, with mnemonics — the 46 kana characters (×2 scripts, plus voiced variants) each get a picture mnemonic, because connecting sounds to memorable images is the fastest proven route to literacy. Input-first, low-stakes quizzing — tapping, listening and repeating; every interaction is graded gently into the SRS. Audio from day one — TextToSpeech pronunciation for every word, phrase and sentence, with adjustable speed. The speaker tries the exact locale, then the bare language, then any installed variant, so it keeps working even when a device only has some voices; if the device has no voice for a language at all it falls back to the network TTS service so nothing is silent.