Comment Descriptivism, folks (Score 2) 287
Published in Science, their paper gives the best-yet estimate of the true number of words in English—a million, far more than any dictionary has recorded (the 2002 Webster's Third New International Dictionary has 348,000) with more than half of the language considered 'dark matter' that has evaded standard dictionaries (PDF).
Umm, no. The phrase "true number of words in English" is sufficiently ill-defined to make the question meaningless. There are two ways people think about whether something is a "true word" in English, but more or less, you need to either rely on an authoritative reference to make that determination (which is not what's happening here), or you note it's existence by some level of usage in practice, and set a somewhat arbitrary bar for how often the word has been used (which is what's happening here.)
As per Zipf's law, etc, tweak that "bar" a little bit, and you'll get quite different results.