- a book, set of books, optical disc, mobile device, or online informational resource containing articles on various topics, usually in alphabetical arrangement, covering all branches of knowledge or, less commonly, all aspects of one subject.
- (initial capital letter) the French work edited by Diderot and D’Alembert, published in the 18th century, distinguished by its representation of the views of the Enlightenment.
- a book, often in many volumes, containing articles on various topics, often arranged in alphabetical order, dealing either with the whole range of human knowledge or with one particular subjecta medical encyclopedia
1530s, “course of instruction,” from Modern Latin encyclopaedia (c.1500), thought to be a false reading by Latin authors of Greek enkyklios paideia taken as “general education,” but literally “training in a circle,” i.e. the “circle” of arts and sciences, the essentials of a liberal education; from enkyklios “circular,” also “general” (from en “in” + kyklos “circle”) + paideia “education, child-rearing,” from pais (genitive paidos) “child” (see pedo-).
Modern sense of “reference work arranged alphabetically” is from 1640s, often applied specifically to the French “Encyclopédie ou Dictionnaire raisonné des Sciences, des Arts, et des Métiers” (1751-65).