From Anglo-Norman and French ides, from Latin īdūs, a fourth-declension pluralia tantum, from the Latin practice of treating most recurring calendrical days as plurals. The Latin term is cognate with Oscan eiduis, both perhaps deriving from an unknown Etruscan term. Middle English and Old French also used the singular form ide.
ides (plural ides)
- (historical, often capitalized) The notional full-moon day of a Roman month, occurring on the 15th day of the four original 31-day months (March, May, Quintilis or July, and October) and on the 13th day of all other months.
- plural of ide