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<snip> According to the Oxford English Dictionary (Second Edition), there are approximately 171,476 words in current use.

However, most native speakers have an active vocabulary between 15,000 and 35,000 words. The Algorithm

We use Stratified Sampling. Instead of testing random words, we divide the language into 5 distinct difficulty bands based on frequency of use:

    1. Core Basics~3,000 words
    2. Intermediate~7,000 words
    3. Advanced~10,000 words
    4. Expert~25,000 words
    5. The Obscure~40,000+ words

"If you answer 2 out of 3 'Intermediate' questions correctly, we estimate you know roughly 66% of the 7,000 words in that band."

Total Score = Σ (Accuracy in Band × Band Size) </clip>