The American Heritage Dictionary of the English Language (AHD) is a dictionary of American English published by Boston publisher Houghton-Mifflin, the first edition of which appeared in 1969. Its creation was spurred by the controversy over the Webster's Third New International Dictionary.

James Parton, the owner of the history magazine American Heritage, was appalled by the "permissiveness" of Webster's Third, published in 1961, and tried to buy the G. and C. Merriam Company so he could undo the changes. When that failed, he contracted with Houghton to publish a new dictionary. The AHD was edited by William Morris and relied on a usage panel of 105 writers, speakers, and eminent persons for usage notes.

The AHD broke ground among dictionaries by using corpus linguistics in compiling word-frequency and other information. The AHD made the innovative step of combining prescriptive elements (how language should be used) and descriptive information (how it actually is used); the latter was derived from text corpora. Citations were based on a million word, three-line citation database prepared by Brown University linguist Henry Kucera.

The first edition appeared in 1969, highly praised for its Indo_European etymologies. In addition to the normally expected etymologies, which for instance trace the word "ambiguous" to a Proto_Indo_European root "ag-", meaning "to drive", the appendices included a seven-page article by Professor Calvert Watkins entitled "Indo-European and the Indo-Europeans" and "Indo-European Roots", 46 pages of entries that are each organized around one of some thousand inferred Proto-Indo-European roots and the English words of the AHD that are understood to have evolved from them. These entries might be called "reverse etymologies": the "ag-" entry there, for instance lists 49 words derived from it, as diverse as "agent", "essay", "purge", "stratagem", "ambassador", "axiom" and "pellagra", along with information about varying routes through intermediate transformations on the way to the contemporary words.

The second edition, published in 1980, omitted the Indo-European etymologies but they were reintroduced in the third edition, published in 1992. The third edition was also a departure for the publisher because it was developed in a database, which facilitated the use of the linguistic data for other applications, such as electronic dictionaries. The fourth edition (2000) added Semitic language materials, including an analogous appendix of roots. As of 2004, it remains the current edition.

The AHD is larger than the desk dictionaries of the time but smaller than Webster's Third New International Dictionary or The Random-House Dictionary of the English Language.

There is a lower-priced college edition with monocolor printing.

External links

• yourDictionary's American Heritage Dictionary online (http://www.yourdictionary.com/ahd/search)
• Bartleby's American Heritage Dictionary online (http://www.bartleby.com/61/)