15 February 2001
This question is only tangentially related to word and phrase origins, but enough people ask it that I thought I’d provide a permanent answer.
This is an indeterminate question. First, there is the problem of what exactly is a word. Are mouse, mice, mousy, and mouselike separate words or just forms of one root word? Is a computer mouse the same word as the rodent? (To demonstrate the difficulty in counting words, over the centuries many scholars have attempted to count how many different words Shakespeare used in his corpus of work. The counts run anywhere from 16,000 to 30,000.)
Second, unlike French, English has no official body to determine what is proper and what is not. English dictionaries are (usually) descriptive in nature, not prescriptive. That is they describe how the language exists and is used, they do not prescribe its use. Just because a word “is not in the dictionary,” doesn’t mean that it is not a legitimate word. It simply means the dictionary editors omitted it for one reason or another.
The Oxford English Dictionary, the largest English-language dictionary, contains some 290,000 entries with some 616,500 word forms in its second edition. Of course, there are lots of slang and regional words that are not included and the big dictionary omits many proper names, scientific and technical terms, and jargon as a matter of editorial policy (e.g., there are some 1.4 million named species of insect alone). All told, estimates of the total vocabulary of English start at around three million words and go up from there.
Of these, about 200,000 words are in common use today. An educated person has a vocabulary of about 20,000 words and uses about 2,000 in a week’s conversation. (These estimates vary widely depending on who is doing the counting, so don’t take them as absolute.)
