ENGLISH LANGUAGE - Number of words in English

The vocabulary of English is undoubtedly very large, but assigning a specific number to its size is more a matter of definition than of calculation — and there is no official source to define accepted English words and spellings in the way that the French Académie française and similar bodies do for other languages.

Archaic, dialectal, and regional words might or might not be widely considered as "English", and neologisms are continually coined in medicine, science, technology and other fields, along with new slang and adopted foreign words. Some of these new words enter wide usage while others remain restricted to small circles.

The General Explanations at the beginning of the Oxford English Dictionary states:
The Vocabulary of a widely diffused and highly cultivated living language is not a fixed quantity circumscribed by definite limits... there is absolutely no defining line in any direction: the circle of the English language has a well-defined centre but no discernible circumference.

The current FAQ for the OED further states:
How many words are there in the English language? There is no single sensible answer to this question. It's impossible to count the number of words in a language, because it's so hard to decide what actually counts as a word.

The Oxford English Dictionary, 2nd edition (OED2) includes over 600,000 definitions, following a rather inclusive policy:
It embraces not only the standard language of literature and conversation, whether current at the moment, or obsolete, or archaic, but also the main technical vocabulary, and a large measure of dialectal usage and slang (Supplement to the OED, 1933).

The editors of Webster's Third New International Dictionary, Unabridged include 475,000 main headwords, but in their preface they estimate the true number to be much higher.

Comparisons of the vocabulary size of English to that of other languages are generally not taken very seriously by linguists and lexicographers. Besides the fact that dictionaries will vary in their policies for including and counting entries, what is meant by a given language and what counts as a word do not have simple definitions. Also, a definition of word that works for one language may not work well in another, with differences in morphology and orthography making cross-linguistic definitions and word-counting difficult, and potentially giving very different results. Linguist Geoffrey K. Pullum has gone so far as to compare concerns over vocabulary size (and the notion that a supposedly larger lexicon leads to "greater richness and precision") to an obsession with penis length.

In December 2010 a joint Harvard/Google study found the language to contain 1,022,000 words and to expand at the rate of 8,500 words per year. The findings came from a computer analysis of 5,195,769 digitised books. Others have estimated a rate of growth of 25,000 words each year.