Prevalence data
Prevalence values come from Brysbaert, Mandera, McCormick & Keuleers' "Word prevalence norms for 62,000 English lemmas," Behavior Research Methods, 51, 467-479. DOI: 10.3758/s13428-018-1077-9.
The public supplementary data reports how widely each lemma was known. As rough guideposts, scores of 0, 1, 1.5, 2, and 2.5 correspond to about 50%, 84%, 94%, 98%, and 99.9% of respondents knowing the word.
Definitions
Short definitions, synonyms, and some example sentences come from WordNet-derived data. They are included to make word pages useful in context, not to replace a full dictionary.
Before commercial use, review the license terms for both the prevalence dataset and WordNet with the relevant rightsholders or legal counsel. This site provides attribution but does not make a legal determination.