The Encyclopædia Britannica (Latin for "British Encyclopaedia") is a general English-language encyclopaedia published by Encyclopædia Britannica, Inc., a privately held company. Articles are aimed at educated adults, and written by about 100 full-time editors and more than 4,000 expert contributors. It is regarded as the most scholarly of encyclopaedias. The Britannica is the oldest English-language encyclopaedia still in print. It was first published between 1768 and 1771 in Edinburgh, Scotland, and grew in popularity and size, its third edition (1797) and supplement (1801) reaching 20 volumes together. Its rising stature helped recruit eminent contributors, and the 9th edition (1875–1889) and the 11th edition (1911) are landmark encyclopaedias for scholarship and literary style. Beginning with the 11th edition, the Britannica shortened and simplified articles to broaden its North American market. In 1933, the Britannica became the first encyclopaedia to adopt "continuous revision", in which the encyclopaedia is continually reprinted and every article updated on a schedule.
The current 15th edition has a unique 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 is 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. The size of the Britannica has remained roughly constant over 70 years, with about 40 million words on half a million topics. Although publication has been based in the United States since 1901, the Britannica has maintained British spelling.