Dictionary:

A dictionary is a book of alphabetically listed words in a specific language, with definitions, etymologies, pronunciations, and other information;[1] or a book of alphabetically listed words in one language with their equivalents in another, also known as a lexicon.[1] 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.
Dictionaries for languages for which the pronunciation of words is not apparent from their spelling, such as the English language, usually provide the pronunciation, often using the International Phonetic Alphabet. For example, the definition for the word dictionary might be followed by the (American English) phonemic spelling: