How it works

The words, the method, the measurement and the research behind them.

The problem

Most vocabulary apps fall short twice.

They teach the wrong words, and they exercise them the wrong way.

The wrong words

A course is only as good as its word list, and most lists are padded. Learning a word no one uses costs the same effort as learning one you will, and pays nothing back.

Old: raimenthearkenpuissant
Obscure: callipygiantintinnabulation
Jargon: ripariananalgesia

Exercised the wrong way

Most apps exercise a word one way: here it is, pick its meaning from four. That is recognition, the first kind of word knowledge to arrive and a long way from using the word. Reviews are spaced by rule of thumb, or not at all, and a word counts as done after a few right answers.

Recognition is only the first kind of knowing.

Nation 2013; Laufer & Goldstein 2004; Cepeda et al. 2006

The words

Chosen by hand.

Every word was judged by a person against one question: would an educated speaker meet this word, and be better off for being able to use it?

Measured, then judged

Each candidate was checked against learner levels and how often it is used, then judged by hand. Frequency alone misses words common in speech, such as leery and jostle.

Cut what doesn’t earn its place

Over a hundred words left the top deck: old and literary words, novelties, Latin tags and words too obscure to use. Field jargon left every deck.

Useful words first

Master English opens with the words a strong reader meets most, such as ubiquitous, ephemeral and nebulous, so the first weeks pay off most.

Written to be learned, not just looked up

One sense: The one worth learning: emollient as soothing an argument, not as skin cream.
A plain definition: Simpler than the word, and able to stand in for it in a sentence.
An example that teaches: You can work out the meaning from the sentence alone.

The method

Knowing a word isn’t one thing.

A word you just looked up feels learned, and a week later it’s often gone. Researchers measure word knowledge in degrees of strength, from recognising a meaning to producing the word unprompted. Vocalibrate measures each one, and moves a word on only when the evidence says it’s ready.

Recognised
You know it when you meet it, on the page or out loud.
The first and weakest kind of knowing. It’s where a word starts, not where it ends.
Recalled
It comes to you from its meaning alone.
Pulling a word from memory is harder than recognising it, and the effort is what makes it stay.
Generated
You can produce it unprompted.
The strongest kind of knowing: the word is there when you need it, not only when you’re asked for it. It comes last on purpose, since putting a new word into sentences too early slows down learning its form.

Yours

A generated word becomes yours once you’ve used it in conversation. Reviews keep it there, each one just before you would forget it, at gaps that grow from days to months as your memory of it strengthens.

Measured, not guessed

An honest measurement, and an honest answer.

Precision means telling you what you actually know. “Not yet” is a normal answer here.

One honest measurement a day: Each word’s first exercise of the study day is the measurement, done cold, before any practice. A pass moves it up; a miss shows you the word and brings it back.
A slip isn’t a miss: A typo, a missing accent or the wrong form of the right word counts, with a note on what to fix. A synonym earns another try.
Sentences, read for meaning: Your sentences are checked by AI for one thing: whether you used the word with its meaning. Mistakes elsewhere become a tip, never a fail.
Every miss teaches: A wrong answer always shows you the word, with its meaning and an example. Often a second, easier question follows, to check what stuck.

Right

Right, with a slip

One slip: it’s spelled occurrence.

Not yet

The word is assiduous.

The science

Built on what memory research has shown, not on what feels productive.

Rereading feels like learning. Generating the word is what makes it stay. Every choice in Vocalibrate follows a finding you can look up.

80%

Exercising a word beats rereading it.

Learners who kept retrieving new foreign words remembered about 80% a week later. Those who stopped once they knew them remembered about a third.

Karpicke & Roediger, Science, 2008

2×

Generating a word beats recognising it.

Practice that asks you to produce the answer had about twice the effect of practice that asks you to pick it, across studies of the testing effect.

Rowland, Psychological Bulletin, 2014

494%

Feedback after a miss matters most.

Seeing the right answer after a wrong one raised what learners kept a week later by 494%. Feedback after a right answer made little difference.

Pashler et al., 2005

839

Spacing is the biggest lever.

Across 839 assessments in 317 experiments, practice spread over days beat the same practice crammed together, and the best gap grows the longer you mean to remember.

Cepeda et al., 2006 and 2008

1 in 4

Learning a word isn’t keeping it.

Across 22 studies of deliberate vocabulary study, learners could produce only about a quarter of the words some time later. Spaced reviews are what turn a word learned into a word kept.

Webb, Yanagisawa & Uchihara, 2020

Sources

Barcroft, J. (2004). Effects of sentence writing in second language lexical acquisition. Second Language Research, 20(4).
Cepeda, N. J., et al. (2006). Distributed practice in verbal recall tasks. Psychological Bulletin, 132(3).
Cepeda, N. J., et al. (2008). Spacing effects in learning: a temporal ridgeline of optimal retention. Psychological Science, 19(11).
Karpicke, J. D., & Roediger, H. L. (2008). The critical importance of retrieval for learning. Science, 319(5865).
Laufer, B., & Goldstein, Z. (2004). Testing vocabulary knowledge: size, strength, and computer adaptiveness. Language Learning, 54(3).
Nation, I. S. P. (2013). Learning Vocabulary in Another Language (2nd ed.). Cambridge University Press.
Pashler, H., et al. (2005). When does feedback facilitate learning of words? Journal of Experimental Psychology: Learning, Memory, and Cognition, 31(1).
Rowland, C. A. (2014). The effect of testing versus restudy on retention: a meta-analytic review of the testing effect. Psychological Bulletin, 140(6).
Tinkham, T. (1993). The effect of semantic clustering on the learning of second language vocabulary. System, 21(3).
Webb, S., Yanagisawa, A., & Uchihara, T. (2020). How effective are intentional vocabulary-learning activities? A meta-analysis. The Modern Language Journal, 104(4).

A few minutes a day

Unhurried, on purpose.

About ten minutes

Three new words a day is the recommended pace. On a day that already holds four times that, new words wait. Today’s new words are tomorrow’s reviews, so the work stays steady.

Similar words apart

Words that look or mean alike are never introduced on the same day, since they blur together.

No streaks, no guilt

Missing a day costs nothing. The words wait, and the schedule picks up where you left off.

Reminders only when it’s worth it

At most one a day, and only when words are ready for you.

What it isn’t

Not a game

No points, leagues or mascots. The reward is noticing the words in your own reading and speech.

Not a word-of-the-day feed

Seeing a word once teaches little that lasts. Each word here is exercised until it is yours, then kept.

Not a crash course

No promises of fluency or a thousand words a month. Every word you finish, you can use.