encyclopedia

American  

[en-sahy-kluh-pee-dee-uh] / ɛnˌsaɪ kləˈpi di ə /

Sometimes encyclopaedia

noun

1. a book, set of books, optical disc, mobile device, or online informational resource containing articles on various topics, usually in alphabetical arrangement, covering all branches of knowledge or, less commonly, all aspects of one subject.

2. Encyclopedia, the French work edited by Diderot and D'Alembert, published in the 18th century, distinguished by its representation of the views of the Enlightenment.

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encyclopedia British  

/ ɛnˌsaɪkləʊˈpiːdɪə /

noun

1. a book, often in many volumes, containing articles on various topics, often arranged in alphabetical order, dealing either with the whole range of human knowledge or with one particular subject

   a medical encyclopedia

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Etymology

Origin of encyclopedia

First recorded in 1525–35; from New Latin encyclopaedia, from Greek enkyklopaidía, a misreading of enkýklios paideía “circular (i.e., well-rounded) education”; see encyclical, pedo- ¹

Explanation

An encyclopedia is a reference work designed to cover all branches and topics of knowledge. We might describe someone who seems to know everything as a "walking encyclopedia." Encyclopedia comes the Greek words for "comprehensive" (cyclo) and "education" (pedia). The first encyclopedias were books (usually in many volumes), but now we have online and electronic encyclopedias. This reference is usually organized alphabetically and covers as many topics as possible. If you're doing research, the encyclopedia is a good place to start.

Example Sentences

Mr. Spencer is a professor of history at Brock University and the editor-in-chief of “The Bloomsbury Encyclopedia of the American Enlightenment.”

From The Wall Street Journal • Nov. 28, 2025

According to the Encyclopedia of Surfing, surfers began using this expression in the 1950s and has been a common expression both in and out of the water ever since.

From Los Angeles Times • Aug. 5, 2024

According to the Holocaust Encyclopedia, Hirschfeld worked to educate and advocate for the rights of gender-nonconforming people.

From Salon • Mar. 15, 2024

“Let’s hide it together,” Dad said and suggested we stash it in the 1933 World Book Encyclopedia Mom got free from the library—under currency.

From "The Glass Castle" by Jeannette Walls

Robots and might as well have spent them at home with the Encyclopedia Tellurica.

From "I, Robot" by Isaac Asimov