see encyclopedia. The Latin spelling survives as a variant because many of the most prominent ones (such as Britannica) have Latin names.
Entries linking to encyclopaedia
encyclopedia n.
1530s, "general 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;" see in + kyklos "circle;" from PIE root *kwel- (1) "revolve, move round") + 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). Related: Encyclopedist.
macropaedia n.
1974, introduced with the 15th edition of the Encyclopaedia Britannica, for the part of the encyclopedia in which information was presented in full essays, from macro- + ending from encyclopaedia.