A dictionary is a book or collection of words in a specific language, often listed alphabetically, with definitions, etymologies, pronunciations, and other information;Webster's New World College Dictionary, Fourth Edition, 2002 or a book of words in one language with their equivalents in another, also known as a lexicon. According to Nielsen 2008 a dictionary may be regarded as a lexicographical product that is characterised by three significant features: (1) it has been prepared for one or more functions; (2) it contains data that have been selected for the purpose of fulfilling those functions; and (3) its lexicographic structures link and establish relationships between the data so that they can meet the needs of users and fulfil the functions of the dictionary.

In many languages, words can appear in many different forms, but only the undeclined or unconjugated form appears as the headword in most dictionaries. Dictionaries are most commonly found in the form of a book, but some newer dictionaries, like StarDict and the New Oxford American Dictionary are dictionary software running on PDAs or computers. There are also many online dictionaries accessible via the Internet.

History

The oldest known dictionaries were Akkadian empire cuneiform tablets with bilingual Sumerian-Akkadian wordlists, discovered in Ebla (modern Syria) and dated roughly 2300 BCE.[http://encarta.msn.com/encyclopedia_761573731/Dictionary.html#p3 Dictionary - MSN Encarta ] The early 2nd millennium BCE Urra=hubullu glossary is the canonical Babylonian version of such bilingual Sumerian wordlists. A Chinese dictionary, the ca. 3rd century BCE Erya, was the earliest surviving monolingual dictionary, although some sources cite the ca. 800 BCE Shizhoupian as a "dictionary", modern scholarship considers it a calligraphic compendium of Chinese characters from Zhou dynasty bronzes. Philitas of Cos (fl. 4th century BCE) wrote a pioneering vocabulary Disorderly Words (Ἄτακτοι γλῶσσαι, ) which explained the meanings of rare Homeric and other literary words, words from local dialects, and technical terms. Apollonius the Sophist (fl. 1st century CE) wrote the oldest surviving Homeric lexicon. The first Sanskrit dictionary, the Amarakośa, was written by Amara Sinha ca. 4th century CE. Written in verse, it listed around 10,000 words. According to the Nihon Shoki, the first Japanese dictionary was the long-lost 682 CE Niina glossary of Chinese characters. The oldest existing Japanese dictionary, the ca. 835 CE Tenrei Banshō Meigi, was also a glossary of written Chinese.