The Encyclopedia Americana (1920)/Deca

DECA (Gr. signifying “ten”), a prefix of frequent occurrence; as in Decapolis, a group of 10 cities; decalogue, the 10 commandments; decametre, the measure of 10 metres, etc. From deca is formed decade, a collection or group of 10. In the calendar of the French Republic the term decade was used to designate the week of 10 days, which were severally named primidi, duodi, tridi, quartidi, quintidi, sextidi, septidi, octidi, nontidi, and decadi. See Calendar.