This article is about the type of reference work. For other uses, see Encyclopedia (disambiguation).

An encyclopedia or encyclopaedia (also spelled encyclopædia, see spelling differences) [1] is a type of reference work or compendium holding a comprehensive summary of information from either all branches of knowledge or a particular branch of knowledge. [2] Encyclopedias are divided into articles or entries, which are usually accessed alphabetically by article name. [3] Encyclopedia entries are longer and more detailed than those in most dictionaries. [3] Generally speaking, unlike dictionary entries which focus on linguistic information about words, encyclopedia articles focus on factual information concerning the subject for which the article is named. [4] [5] [6] [7]

Encyclopedias have existed for around 2,000 years; the oldest still in existence, Naturalis Historia, was written starting in ca. AD 77 by Pliny the Elder and was not fully revised at the time of his death in AD 79. The modern encyclopedia evolved out of dictionaries around the 17th century. Historically, some encyclopedias were contained in one volume, whereas others, such as the Encyclopædia Britannica, the Enciclopedia Italiana (62 volumes, 56,000 pages) or the world's largest, Enciclopedia universal ilustrada europeo-americana (118 volumes, 105,000 pages), became huge multi-volume works. Some modern encyclopedias, such as Wikipedia, are electronic and often freely available.


Title page of "Lucubrationes..." 1541 edition, the first book to use the word encyclopedia in the title

The word encyclopedia comes from the Koine Greek ἐγκύκλιος παιδεία, [8] transliterated enkyklios paideia, meaning "general education" from enkyklios (ἐγκύκλιος), meaning "circular, recurrent, required regularly, general" [9] and paideia (παιδεία), meaning "education, rearing of a child"; [10] it was reduced to a single word due to an error [11] by copyists of Latin manuscripts. Together, the phrase literally translates as "complete instruction" or "complete 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 [12]

Copyists of Latin manuscripts took this phrase to be a single Greek word, enkyklopaidia, with the same meaning, and this spurious Greek word became the New Latin word "encyclopaedia", which in turn came into English. Though the notion of a compendium of knowledge dates back thousands of years, the term was first used in the title of a book in 1517 by Johannes Aventinus: Encyclopedia orbisque doctrinarum, hoc est omnium artium, scientiarum, ipsius philosophiae index ac divisio, and in 1538 by Joachimus Fortius Ringelbergius, Lucubrationes vel potius absolutissima kyklopaideia ( Basel, 1538).

Title page of Skalich's Encyclopaedia, seu orbis disciplinarum, tam sacrarum quam prophanarum, epistemon from 1559, first to use the word encyclopaedia as a noun in the title

The word encyclopaedia was first used as a noun in the title of his book by the Croatian encyclopedist Pavao Skalić in his Encyclopaedia seu orbis disciplinarum tam sacrarum quam prophanarum epistemon (Encyclopaedia, or Knowledge of the World of Disciplines, Basel, 1559). One of the oldest vernacular uses was by François Rabelais in his Pantagruel in 1532. [13] [14] Several encyclopedias have names that include the suffix -p(a)edia, e.g., Banglapedia (on matters relevant for Bengal).

In British usage, the spellings encyclopedia and encyclopaedia are both current. [15] In American usage, only the former is commonly used. [16] The spelling encyclopædia—with the æ ligature—was frequently used in the 19th century and is increasingly rare, although it is retained in product titles such as Encyclopædia Britannica and others. The Oxford English Dictionary (1989) records encyclopædia and encyclopaedia as equal alternatives (in that order), and notes the æ would be obsolete except that it is preserved in works that have Latin titles. Webster's Third New International Dictionary (1997–2002) features encyclopedia as the main headword and encyclopaedia as a minor variant. In addition, cyclopedia and cyclopaedia are now rarely used shortened forms of the word originating in the 17th century.