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.

---

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

---

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. Henderson is a research fellow with Stanford University’s Hoover Institution and editor of the Concise Encyclopedia of Economics.

From The Wall Street Journal • Oct. 13, 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

Mr. Haynes, of Portland, debuted in the W.W.F., which is today called World Wrestling Entertainment, in 1986, according to the book “WWE Encyclopedia: The Definitive Guide to World Wrestling Entertainment.”

From New York Times • Feb. 11, 2024

I had no idea what the Progressive Era was, and back in the office, I got out the World Book Encyclopedia.

From "The Glass Castle" by Jeannette Walls

Easier than solving an Encyclopedia Brown-level clue in Book Scavenger.

From "Book Scavenger" by Jennifer Chambliss Bertman