The Oxford English Dictionary is the accepted authority on the evolution of the English language since 1150. It is an unsurpassed 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 includes all common words of speech and literature, including scientific/technical terms and foreign words in general use. The library owns several editions of the OED, both print and online.