Dictionary is a book that contains a selected list of words arranged in alphabetical order. It explains their meanings and gives information about them. In a dictionary, a person can look up a word quickly, discover what it means, and learn how it is pronounced. Most modern dictionaries describe the facts of a language as educated speakers and writers use it. They are called descriptive dictionaries because a dictionary editor does not change the facts of a language. Many older dictionaries tried to prescribe rules, some of which did not agree with the way people commonly talked or wrote. These books are called prescriptive dictionaries.