Dictionary is a book that provides an alphabetical list of the words of a language and an explanation of their meaning and use. It may also give the origin and pronunciation of each word and may quote passages to illustrate its use in speech and literature. Some dictionaries include rules of grammar and spelling and lists of proper names and of abbreviations.
The most complete dictionaries are unabridged. In addition to listing the ordinary words of a language, unabridged dictionaries include obscure and foreign words, technical terms, and idiomatic expressions, with detailed definitions and illustrations for each entry. Many people find it convenient to use a smaller abridged dictionary, which lists common words and brief definitions of them.
The word "dictionary" is loosely used to refer to any specialized reference book that consists of a series of entries arranged in alphabetical order. Among such works are Black's Law Dictionary, Grove's Dictionary of Music and Musicians, and the Dictionary of American Biography. Bilingual dictionaries list the words of a language and give their equivalents in another language. A thesaurus is a dictionary that lists synonyms and antonyms. It need not be alphabetical. Geographical dictionaries are known as gazetteers.