The Encyclopædia Britannica (Latin for "British Encyclopaedia"), formerly published by Encyclopædia Britannica, Inc., is a general knowledge English-language encyclopaedia. It was written by about 100 full-time editors and more than 4,000 contributors. The 2010 version of the 15th edition, which spans 32 volumes and 32,640 pages, was the last printed edition.
The Britannica is the English-language encyclopaedia/encyclopedia that was in print for the longest time: it lasted 244 years. It was first published between 1768 and 1771 in the Scottish capital of Edinburgh, as three volumes. (This first edition is available in facsimile.) The encyclopaedia grew in size: the second edition was 10 volumes, and by its fourth edition (1801–1810) it had expanded to 20 volumes. Its rising stature as a scholarly work helped recruit eminent contributors, and the 9th (1875–1889) and 11th editions (1911) are landmark encyclopaedias for scholarship and literary style. Beginning with the 11th edition and following its acquisition by an American firm, the Britannica shortened and simplified articles to broaden its appeal to the North American market. In 1933, the Britannica became the first encyclopaedia to adopt "continuous revision", in which the encyclopaedia is continually reprinted, with every article updated on a schedule. In March 2012, Encyclopædia Britannica, Inc. announced it would no longer publish printed editions, and would focus instead on Encyclopædia Britannica Online.
The 15th edition had a three-part structure: a 12-volume Micropædia of short articles (generally fewer than 750 words), a 17-volume Macropædia of long articles (two to 310 pages), and a single Propædia volume to give a hierarchical outline of knowledge. The Micropædia was meant for quick fact-checking and as a guide to the Macropædia; readers are advised to study the Propædia outline to understand a subject's context and to find more detailed articles. Over 70 years, the size of the Britannica has remained steady, with about 40 million words on half a million topics. Though published in the United States since 1901, the Britannica has for the most part maintained British English spelling.