A radical and controversial departure from its more encyclopedic and proscriptive predecessors, Merriam Webster's Third New International Dictionary has slowly established itself as one of America's premier lexicographical works, containing over 450,000 vocabulary entries. This electronic version, offered by Chadwyck-Healey, allows users to search the dictionary by Headword, Keyword, Etymology Keyword, Author/Quotation Keyword, and/or Part of Speech.
For the student of contemporary American English, Webster's Third Unabridged is an essential tool because it is more than 3 times the scope of the Tenth Collegiate. It is an authoritative source on the language as actually used and contains etymologies, definitions of the term as used since 1755, and over 200,000 illustrative quotations, mostly drawn from contemporary sources.
The dictionary does not attempt to present a historical record of the English language. Rather, it covers in a single volume the current vocabulary of standard written and spoken English. New terms or new uses of existing terms are therefore included at the expense of obsolete ones. The cut-off point is set at 1755 and is informed by usefulness: words obsolete before this time, unless found in the well-known works of major authors, are omitted.