décade

Décade is a French noun that denotes a period of ten years. In contemporary usage, the term prefers emphasis most often falls on the related word décennie, which is the standard term for a ten-year span. Décade tends to appear in more formal, literary, or historical contexts, and is less common in everyday speech.

In addition to its modern sense as ten years, décade has historical usages referring to a ten-day period. In certain calendars and historical literatures, a décade was a unit of time equal to ten days, such as in the context of the French Revolutionary Calendar, where time was occasionally divided into ten-day blocks. This sense is rarely used in modern discourse outside of historical discussion.

Etymology traces décade to the prefix deka- meaning ten, from Greek deka-, via Latin and Old French derivations. The word entered French with meanings tied to ten-unit groups and later specialized to signify decades, with the ten-day sense surviving in scholarly descriptions of historical calendars.

Usage notes: while décade is understood to mean ten years, most contemporary writing prefers décennie for clarity. Décade may be used when referring to a specific ten-year era in a stylistically marked way, or when recounting historical periods in older texts. When discussing time spans in general, décennie is typically the clearer and more common choice. See also décennie and the historical sense of décade as a ten-day period.