1. A reference book containing an alphabetical list of words, with information given for each word, usually including meaning, pronunciation, and etymology.
2. A book listing the words of a language with translations into another language.
3. A book listing words or other linguistic items in a particular category or subject with specialized information about them: a medical dictionary.
4. Computer Science.
   1. A list of words stored in machine-readable form for reference, as by spelling-checking software.
   2. An electronic spelling checker.

[Medieval Latin dictiōnārium, from Latin dictiō, dictiōn-, diction. See diction.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.