A dictionary is a reference book that contains an alphabetical list of words with their definitions and pronunciations. Dictionaries provide guidelines on how to use the book, including how words are arranged, abbreviations used, and pronunciation symbols. To look up a word, the user finds the letter section, scans the pages following alphabetical order and guide words, and reads the entry which defines the word, its pronunciation and part of speech. Online dictionaries provide a similar service digitally through search engines.