DECADE (from Gr. 5/ca, ten), a group or series containing ten members, particularly a period of ten years. In the new calendar made at the time of the French Revolution in 1793, a decade of ten days took the place of the week. The word is also used of the divisions containing ten books or parts into which the history of Livy was divided.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)