They typical unabridged dictionary contains approximately 350,000 words: if inferred forms (for example, adding -S to nouns and -ED or -ING to verbs) are added, the total stockpile of English words and phrases probably exceeds 500,000. Large as this number is, it is easily topped by a less-well-known stockpile of words: the surnames of United States residents. As of June 1, 1964, there were nearly 1,100,000 different surnames for which Social Security cards had been issued since the program began 28 years earlier.
Eckler, A. Ross
"The Terminal Man,"
Word Ways: Vol. 7
, Article 17.
Available at: http://digitalcommons.butler.edu/wordways/vol7/iss3/17