Oxford English Dictionary (OED) This link opens in a new window
Oxford English Dictionary is the accepted authority on the evolution of the English language over the last millennium. It is a guide to the meaning, history, and pronunciation of over half a million words, both present and past. It traces the usage of words through 2.5 million quotations from a wide range of international English language sources, from classic literature and specialist periodicals to film scripts and cookery books.
The OED covers words from across the English-speaking world, from North America to South Africa, from Australia and New Zealand to the Caribbean. It also offers the best in etymological analysis, listings of variant spellings, and shows pronunciation using the International Phonetic Alphabet.