An encyclopedia (also spelled encyclopaedia, encyclopedia or encyclopædia) is a type of reference work – a compendium holding a summary of information from either all branches of knowledge or a particular branch of knowledge. Encyclopedias are divided into articles or entries, which are usually accessed alphabetically by article name. Encyclopedia entries are longer and more detailed than those in most dictionaries. Generally speaking, unlike dictionary entries, which focus on linguistic information about words, encyclopedia articles focus on factual information to cover the thing or concept for which the article name stands. (Wikipedia, 2014)
The word encyclopedia comes from the Koine Greek transliterated enkyklios paideia, meaning "general education": enkyklios, meaning "circular, recurrent, required regularly, general" + paideia, meaning "education, rearing of a child"; it was reduced to a single word due to an error by copyists of Latin manuscripts. Together, the phrase literally translates as "complete instruction" or "complete knowledge.".Ibid.
The word encyclopedia, which to us usually means a large set of books, descends from a phrase that involved coming to grips with the contents of such books. The Greek phrase is enkuklios paideia, made up of enkuklios, "cyclical, periodic, ordinary," and paideia, "education," and meaning "general education." Copyists of Latin manuscripts took this phrase to be a single Greek word, enkuklopaedia, with the same meaning, and this spurious Greek word became the New Latin word encyclopaedia, coming into English with the sense "general course of instruction," first recorded in 1531. In New Latin the word was chosen as the title of a reference work covering all knowledge. The first such use in English is recorded in 1644. (answers.com, 2014)