The Oxford English Dictionary (OED) is the main historical dictionary of the English language, published by the Oxford University Press. It traces the historical development of the English language, providing a comprehensive resource to scholars and academic researchers, as well as describing usage in its many variations throughout the world. The second edition came to 21,728 pages in 20 volumes, published in 1989.
Work began on the dictionary in 1857, but it was not until 1884 that it began to be published in unbound fascicles as work continued on the project, under the name of A New English Dictionary on Historical Principles; Founded Mainly on the Materials Collected by The Philological Society. In 1895, the title The Oxford English Dictionary (OED) was first used unofficially on the covers of the series, and in 1928 the full dictionary was republished in ten bound volumes. In 1933, the title The Oxford English Dictionary fully replaced the former name in all occurrences in its reprinting as twelve volumes with a one-volume supplement. More supplements came over the years until 1989, when the second edition was published. Since 2000, a third edition of the dictionary has been underway, approximately half of which is now complete.
The first electronic version of the dictionary was made available in 1988. The online version has been available since 2000, and as of April 2014 was receiving over two million hits per month. The third edition of the dictionary will probably only appear in electronic form; Nigel Portwood, chief executive of Oxford University Press, thinks it unlikely that it will ever be printed.
As a historical dictionary, the Oxford English Dictionary explains words by showing their development rather than merely their present-day usages. Therefore, it shows definitions in the order that the sense of the word began being used, including word meanings which are no longer used. Each definition is shown with numerous short usage quotations; in each case, the first quotation shows the first recorded instance of the word that the editors are aware of and, in the case of words and senses no longer in current usage, the last quotation is the last known recorded usage. This allows the reader to get an approximate sense of the time period in which a particular word has been in use, and additional quotations help the reader to ascertain information about how the word is used in context, beyond any explanation that the dictionary editors can provide.
The format of the OED's entries has influenced numerous other historical lexicography projects. The forerunners to the OED, such as the early volumes of the Deutsches Wörterbuch, had initially provided few quotations from a limited number of sources, whereas the OED editors preferred larger groups of quite short quotations from a wide selection of authors and publications. This influenced later volumes of this and other lexicographical works.
According to the publishers, it would take a single person 120 years to "key in" the 59 million words of the OED second edition, 60 years to proofread them, and 540 megabytes to store them electronically. As of 30 November 2005, the Oxford English Dictionary contained approximately 301,100 main entries. Supplementing the entry headwords, there are 157,000 bold-type combinations and derivatives; 169,000 italicized-bold phrases and combinations; 616,500 word-forms in total, including 137,000 pronunciations; 249,300 etymologies; 577,000 cross-references; and 2,412,400 usage quotations. The dictionary's latest, complete print edition (second edition, 1989) was printed in 20 volumes, comprising 291,500 entries in 21,730 pages. The longest entry in the OED2 was for the verb set, which required 60,000 words to describe some 430 senses. As entries began to be revised for the OED3 in sequence starting from M, the longest entry became make in 2000, then put in 2007, then run in 2011.