Four r/languagelearning threads in a year ask for the same thing in…
Four r/languagelearning threads in a year ask for the same thing in different words: let me keep my own word list and generate sentences that use only words I already know. One says outright they would pay 'any price'. In the same window Rosetta Stone withdrew its lifetime licence and the top thread is someone saying they cannot afford four subscriptions.
What is the idea?
Keep the words you personally collected — from a novel, a Wikipedia page, a conversation — and get back sentences, short readings and quizzes built only from words you already have, so nothing you read contains a word you cannot decode.
Why would anyone bother?
Someone learning Turkish from novels, someone who reads Wikipedia in their target language, a person who says their vocabulary would jump if only they could keep it in one place. What they get back is reading material at exactly their level, which is the thing every learner is told to find and nobody can.
What is missing today?
Anki stores your words and never generates anything; the chat assistants generate endlessly and forget your list the moment the window closes; the graded-reader publishers pick the vocabulary for you. Nobody joins your own collected list to generated material at your boundary — which is what all four askers describe.
What makes this one different?
Do not build a language app. Build the boundary: import your list from Anki or a photo of your notebook, and every morning produce one 150-word story that contains zero words outside it, plus the five words you are closest to being ready for. Cold start (Chinese): 小红书「背单词 记不住」「原版书 生词」标签与考研/雅思词汇打卡群; (English): the r/languagelearning threads themselves and the Anki subreddit, where the same request appears as an add-on wish.
What is the sharpest thing about it?
'Write me a sentence using exactly these 40 words and nothing harder' is a constraint-satisfaction task that was hopeless for template systems and trivial for a language model. The i+1 idea is fifty years old in pedagogy; being able to actually generate at a learner's exact known-word boundary, on demand, is new.
What could kill it?
This is the most copyable idea on this batch: it is an Anki add-on plus one prompt, and several already exist in rough form. The audience also self-selects for people who will build it themselves, and Duolingo or Anki shipping it natively ends the category in one release. Weakest of today's findings and marked as such.
Who pays, and for what?
A self-taught learner who is already paying for one subscription and resents paying for four — priced as one, replacing the reading-material problem rather than the drilling problem.
What is the main risk?
Trivially copyable, and one Anki release or one Duolingo feature away from irrelevance; the strongest version may simply be an add-on, not a business.
What did real people actually say?
Verbatim from the public sources linked above, not paraphrased: “Is there an app or site where you can save your own vocab to a library, and then it creates sentences with them?” — reddit r/languagelearning (7 pts / 16 comments) “I really need this, I think my vocabulary will shoot up instantly significantly if I have something like this. Free or cheap or any price.” — reddit r/languagelearning (8 comments) “I don't have the money to be paying multiple subscriptions, so, is there an app or site that do what rosetta stone used to?” — reddit r/languagelearning (16 pts / 35 comments, 2 days old) “Is there an app which either integrates with Safari on iPhone or has an integrated web-browser where you can mark whatever word you want and create a flashcard for it?” — reddit r/languagelearning
How much work is it?
about two weeks of work
Where does the evidence come from?
https://old.reddit.com/r/guitarlessons+learnart+languagelearning+piano+singing/search?q=%22is+there+an+app%22&restrict_sr=on&sort=top&t=year
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