Key evidence & numbers
| Counting unit | Estimate at age 20 | Meaning |
|---|---|---|
| Lemmas | 42,000 | Entries that combine inflected forms, such as walk and walked. |
| Word families | 11,100 | Broader groups that also combine related derived words. |
Source: original estimates table. The full dataset contained 221,268 individuals; that is not the native-English or age-specific N.
What affects it?
Age, education, language experience and counting rules affect the estimate. Study
Try the related free test
Vocabulary size test
Test yourself: vocabulary. Follow the instructions about real and invented words; treat the result as an estimate for that word list.
Common questions
Does this estimate apply to every adult?
No. The age, language and volunteer sample limit the comparison.
Why do other sources give smaller totals?
Check their counting unit and what “knowing” requires.
Is vocabulary size the same as intelligence?
This task estimates word knowledge. It does not establish a person's overall intelligence.
Sources
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