Alternative spellings

• encyclopædia (dated, chiefly UK)
• encyclopedia (US, Canada, accepted in Australian and International English, and is also common in British English)

Noun

Singular encyclopaedia

Plural encyclopaedias or encyclopaediae

encyclopaedia (plural encyclopaedias or encyclopaediae)

1. (chiefly UK) A reference work (often in several volumes) containing in-depth articles on various topics (often arranged in alphabetical order or by category) dealing with a wide range of subjects or with some particular specialty

An encyclopedia (also spelled encyclopaedia or encyclopædia) is a type of reference work, a compendium holding information from either all branches of knowledge or a particular branch of knowledge.

Encyclopedias are divided into articles. The articles in an encyclopedia are usually accessed alphabetically by article name (or sometimes by theme). Unlike dictionary entries which are about the often many linguistic, etymological and usage aspects of their entry's word or term, each encyclopedia article's subject is a single concept that is referred to by the article name.

Encyclopedias have existed for around 2,000 years; the oldest still in existence, Naturalis Historia, was written in Roman times by Pliny the Elder. The modern encyclopedia evolved out of dictionaries around the 17th century. Historically, some encyclopedias were contained in one volume, but some, such as the Encyclopaedia Britannica, became huge multi-volume works. Some modern encyclopedias are electronic and are often freely available.

The word encyclopaedia comes from the Koine Greek "ἐγκυκλοπαιδεία", from Greek "ἐγκύκλιος παιδεία", transliterated "enkyklios paideia": "enkyklios" (ἐγκύκλιος), meaning "circular, round" + "paideia" (παιδεία), meaning "education, rearing of a child". Together, the phrase literally translates as a "well rounded education" or "general knowledge".

Indeed, the purpose of an encyclopedia is to collect knowledge disseminated around the globe; to set forth its general system to the men with whom we live, and transmit it to those who will come after us, so that the work of preceding centuries will not become useless to the centuries to come; and so that our offspring, becoming better instructed, will at the same time become more virtuous and happy, and that we should not die without having rendered a service to the human race in the future years to come. — Diderot