A dictionary, also called a lexicon, wordbook, or vocabulary, is a collection of words in one or more specific languages, often listed alphabetically, with usage information, definitions, etymologies, phonetics, pronunciations, and other information; 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:
- it has been prepared for one or more functions;
- it contains data that have been selected for the purpose of fulfilling those functions; and
- its lexicographic structures link and establish relationships between the data so that they can meet the needs of users and fulfill the functions of the dictionary.