An encyclopedia, conversation dictionary, encyclopedia, encyclopedia or encyclopedia is a reference work that has the ambition to summarize all knowledge, either in general or in a specific area. The encyclopedia is in the form near the dictionary, with articles of varying length on a wide range of topics. Both consist of a summary of human knowledge, usually sorted alphabetically. In many cases, the dictionary and the encyclopedia coexist within the same work, regardless of whether the work consists of one or more volumes.
The term encyclopedia comes from the Greek encyclopaedia paideia, literally "rounded education" or "knowledge that forms a circle", meaning "general education". Variant of paideia (παιδεία), is found in the meaning "education, rearing, of a child". It was not until the 18th century that the term "encyclopedia" began to be used to refer to the collections of knowledge that are today associated with the word. Since then, many encyclopedias internationally have used -pedi or -pedia as a suffix to indicate that the work is an encyclopedia.
The Latin term was first used in Swedish, but during the second half of the 19th century the more Swedish "encyclopedia" began to be used. At the beginning of the 20th century, "encyclopedias" appeared, to indicate that an encyclopedia usually consists of several volumes.
Unlike dictionaries, which contain purely formal information about words, such as spelling and inflection, encyclopedias treat each subject fairly thoroughly, often with illustrations or maps, bibliographies and statistics. Both have, however, traditionally been written by paid subject matter experts.
An encyclopedia is defined by four major elements: its subject area, its breadth, its structure and its method of production.
its subject area can, but need not be, comprehensive, with articles on subjects in all areas, such as the Encyclopædia Britannica or the Brockhaus Enzyklopädie. They may also specialize in specific areas, such as a medical or philosophical encyclopedia. There are variants where the subject selection is wide, but the articles are written from a special cultural or ethnic point of view, for example the Encyclopaedia Judaica, or where the articles have a clear political angle, for example the Great Soviet Encyclopedia. In addition, there are encyclopedias whose emphasis is on topics related to its country of production, such as the Swedish National Encyclopedia.
its scope is limited by the intended target group's need for knowledge in the chosen subject area. The scope of the work varies both in the number of volumes and the length of the articles.
its structure is crucial to how useful reference literature is. Throughout history, there have been two main methods of organizing printed encyclopedias: alphabetically and hierarchically. The former method has been the most common, especially in general encyclopedias. With the electronic encyclopedias, the opportunity has arisen to structure the articles in several ways at the same time. In addition, new search methods, indexing and cross-references have been developed. In Denis Diderot's Encyclopédie, the structure of the encyclopedia is emphasized with the help of a quote by Horace: "Tantum series juncturaque pollet, tantum de medio sumptis accedit honoris!" (roughly "What beauty can be added to everyday subjects through order and connections.")
its production method has been developed from experts who write about their respective topics under the guidance of an editor, for the production of a series of printed volumes, to several alternative (often technical) solutions for collecting, verifying, summarizing and presenting the information. Projects such as Everything2, Microsoft Encarta, h2g2 and Wikipedia are examples of new such forms of encyclopedias.