The British-based Britannica World Encyclopedia was first published in 1867 and since then, has been in continuous publication. There are fifteen editions of the Britannica World Dictionary, which was updated in 1989 and 2010 respectively. The 15th edition was reorganized in 1985, and the previous nine were reprinted. It is the current version of the dictionary. However, previous editions were revised annually, so they differed from the current edition.

The current incarnation of the Britannica World Encyclopedia is the fifteenth edition. It was published as a separate two-volume index, and comes in three volumes. The Macropaedia and Micropaedia were combined into a single encyclopedia. Some medium-length articles were moved into the Micropaedia, while others were consolidated into longer articles. The encyclopedia now contains more than a billion words.

The ninth edition was edited by Thomas Spencer Baynes, a Scottish geologist. His portrait hangs in the Senate Room at the University of St Andrews in Scotland. Dale Hoiberg, a sinologist and Senior Vice-President of Britannica, is editor-in-chief of the 15th edition. Previously, the encyclopedia was edited by Warren E. Preece, who served as editor-in-chief from 1968 to 1975.