text: Encyclopedia or Encyclopaedia, reference work that provides information on a range of subjects. Encyclopedias can encompass many areas of interest, or they can focus on a particular field of study, such as a geographic area, an ethnic group, a time period, or an academic discipline. Most encyclopedias have hundreds or thousands of articles, each addressing a distinct topic. Many of the articles contain illustrations, maps, photographs, and other media elements that help readers understand concepts. For centuries encyclopedias were published as multivolume sets of books, but in the late 20th century they appeared in new formats, such as CD-ROM, digital video disc (DVD), and on the Internet. \n\nThe term encyclopedia comes from the Greek words enkyklios paideia, meaning “comprehensive education” and originally signifying instruction in all branches of knowledge, or a comprehensive education in a specific subject. This concept gave rise to the idea of collecting the materials for such instruction into a single work, in which the contents and relations of the various arts and sciences would be explained systematically. Attempts to produce books of this kind were made more than 2,000 years ago, although the name encyclopedia was not given to such works until the 16th century.