Deca

Deca (Gr., signifying 'ten'), a prefix of frequent occurrence: as in Decapolis, a group of ten cities; decalogue, the ten commandments; decamètre, a measure of ten mètres, &c. From deca is formed decade, a collection or group of ten. In the calendar of the French Republic the term decade was used to designate their week of ten days, the various days of which were named primidi, duodi, tridi, quartidi, quintidi, sextidi, septidi, octidi, nonidi, and decadi. See CALENDAR.