ides

UK: /aɪdz/ US: (īdz)

WordReference Random House Unabridged Dictionary of American English © 2026

ides  (īdz), n. (used with a sing. or pl. v.)

1. Time, Antiquity (in the ancient Roman calendar) the fifteenth day of March, May, July, or October, and the thirteenth day of the other months.

• Latin
• Latin īdūs (feminine plural); replacing Middle English idus
• Old French
• Middle English 1300–50

-ides, 

1. a Greek plural suffix appearing in scientific names:
   cantharides.

• Greek, plural of -is, suffix of source or origin. See -id¹

Collins Concise English Dictionary © HarperCollins Publishers::

ides / aɪdz/ noun

1. (functioning as singular) (in the Roman calendar) the 15th day in March, May, July, and October and the 13th day of each other month
   See also calends, nones

Etymology: 15th Century: from Old French, from Latin īdūs (plural), of uncertain origin