Sentence mining means saving sentences from your reading or listening that contain one new word, then reviewing them as flashcards. It comes from self-taught learners rather than researchers, but it rests on solid ground: retrieval practice works, and a real sentence shows how a word is used. Studies find one example sentence adds little to learning the meaning itself.
Where does sentence mining come from?
The idea spread through online learning communities. In 2006 the blogger behind All Japanese All The Time, writing as Khatzumoto, described learning Japanese through 10,000 sentences entered into a spaced repetition program. He suggested that about 50 a day was manageable, that 15–25 was fine, and that the sentences should not be memorised word for word: seeing and reading them repeatedly over time would do the work.
Today the best-known description comes from Refold, which defines sentence mining as finding sentences with unknown words in the material you are reading or watching, looking the words up, and saving them as flashcards. Its rule of thumb is to look for one-target sentences, with one unknown word and at most two, and to skip sentences with three or more. It also warns that saving 30 or more cards in a session is easy, and that cards you cannot keep up with pile up.
Does a sentence on a flashcard help you learn the word?
For learning what a word means, the evidence for adding a single sentence is weaker than mining advocates often suggest. For remembering, the flashcard part is strongly supported.
| Study | What was compared | Result |
|---|---|---|
| Webb (2007) | Japanese learners of English studying word pairs or a single glossed sentence, tested in 10 different ways | No significant difference; a single sentence may have little effect on vocabulary knowledge |
| Prince (1996) | Learning words with translations or in English context | Translations led to more words learned, but weaker learners struggled to use them in new sentences; the author suggests combining both |
| Laufer & Shmueli (1997) | Words in isolation, in one sentence, in a text or in an expanded text | Words in lists and single sentences were remembered better than words in texts; first-language glosses beat English ones |
| Karpicke & Roediger (2008) | 40 students learning 40 Swahili–English pairs, testing themselves or restudying | About 80% recalled a week later with repeated testing, against 33–36% when items were dropped from testing |
| Folse (2006) | One fill-in-the-blank exercise, three, or writing an original sentence | Three fill-in-the-blank exercises gave the best retention; the number of retrievals mattered more than depth of processing |
Put together: what makes a card work is retrieving the answer, again and again over time, and a translation in your own language helps the first meeting stick. A 2020 meta-analysis by Webb, Yanagisawa and Uchihara found average gains of 60.1% on immediate meaning-recall tests for word-focused activities such as flashcards and word lists, falling to 39.4% on delayed tests, so even good cards need repeat visits.
The sentence earns its place in other ways. It shows grammar and the words a term keeps company with, which Webb's single sentence was not enough to teach but repeated sentences from your reading may be. It gives the gap for a fill-in-the-blank review. And it reminds you where you met the word, which is part of what Prince's weaker learners were missing.
How do you choose a sentence worth mining?
- One new word. Everything else should already be clear, so the sentence explains the word rather than adding to the confusion.
- Short and complete. It should make sense on its own, without the paragraph around it.
- A word that will come back. Common words and words your story keeps using repay the effort; a one-off rarity can wait.
- Meaning carried by the context. The best sentences give the word a job you can picture.
A sentence from a free A1 chapter that works for a reader who knows the other words:
Lucía vive en un piso pequeño encima de la panadería de Tomás.
How easy is it to find sentences like that? We took a list of the 1,000 most frequent word forms from one half of the Contos library and checked how many sentences in the other half had exactly one form outside it:
| Level | Spanish: one unfamiliar form | Spanish: two or more | French: one unfamiliar form | French: two or more |
|---|---|---|---|---|
| A1 | 34% | 19% | 34% | 14% |
| A2 | 33% | 36% | 37% | 28% |
| B1 | 21% | 69% | 24% | 65% |
| B2 | 19% | 70% | 18% | 70% |
For a reader with roughly a thousand words, about a third of A1 and A2 sentences are ideal mining material, but at B1 and B2 most sentences contain two or more unfamiliar forms. That is the coverage problem from another angle: mining works best in text that is already mostly easy. Counting exact forms is strict, since a new ending on a known verb counts as unfamiliar, so a real reader will do somewhat better.
How does sentence mining work in Contos?
Contos builds the mining step into reading. Tap a word for its meaning and you can save it as a flashcard; the card keeps the sentence you found it in. In review, a card first asks for the meaning, then for a while shows its sentence with the word blanked out for you to fill in, and later asks you to produce the word from its meaning. The intervals follow the ladder on our spaced repetition page.
- Save selectively. Refold's warning applies: a dozen well-chosen cards a day beat fifty you will never review.
- Prefer words that return. In a serialized story, a word that appears in chapter 1 and again in chapter 2 will probably keep coming. Our page on frequency lists explains why common words pay off first.
- Let reading do the rest. Cards make the first meeting stick; the next chapter shows the word in a new sentence, which a single card cannot.
Read a free chapter and save three sentences that each have one new word.
Read free in your browserFrequently asked questions
Is sentence mining better than learning word lists?
Not for learning bare meanings: Webb found a single glossed sentence did no better than a word pair, and Laufer and Shmueli found lists and single sentences beat longer texts. Sentences help with usage and give you material for fill-in-the-blank reviews, so many learners combine a translation with a sentence.
What is a one-target sentence?
A sentence with exactly one word you don't know. Refold calls these 1T sentences and suggests mining sentences with one unknown word, or two at most, because the rest of the sentence then explains the new word instead of adding confusion.
How many sentences should I mine a day?
As many as you can keep reviewing. Khatzumoto thought about 50 a day was manageable and 15–25 was fine, and Refold warns that cards pile up quickly. There is no research-based number; start small, with ten or so, and add more if your reviews stay under control.
Do I need Anki for sentence mining?
No. Any spaced repetition tool that lets you store a sentence works. In Contos, the sentence is saved with the card automatically when you save a tapped word, and reviews include fill-in-the-blank cards built from it.
Should I memorise the whole sentence?
No. Even Khatzumoto advised against memorising sentences word for word. The sentence is there to show the word in use; what you need to recall is the word and its meaning.