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Liz Potter
Written by Liz Potter


in the ancient Roman calendar, the 15th of March, May, July, and October, and the 13th of the other months

View the full definition in the Macmillan Dictionary.

Origin and usage

The noun ides was borrowed from the Latin ‘Idus’ in its feminine plural form. It refers to the third of three marker days in the Roman calendar, and first appeared in Old English towards the end of the first millennium.


Many of us are aware of the word ides thanks to Shakespeare’s ‘Julius Caesar’, in which the eponymous leader is warned by a soothsayer to ‘Beware the ides of March’. Caesar ignores the advice, along with that of his wife Calpurnia, and is duly murdered on that day by a group of conspirators led by his former friend and ally Brutus. It is probably because of its appearance in Shakespeare’s play and subsequent life as part of a catchphrase that ides is a relatively familiar word in English. We remember the Ides of March but may forget or not know that all the other months had ides too: as the definition above shows, the 15th in May, July and October and the 13th in all the other months. Two years before his death Caesar had been responsible for the reform of the calendar and the introduction of a new one that bears his name. The Julian calendar was used in most of Europe and the Americas before gradually being replaced by the Gregorian calendar devised in the late 16th century. The entry for ides comes from our crowdsourced Open Dictionary and was submitted by a reader in Argentina last year. You can submit words and phrases to the Open Dictionary here.


Caesar: What say’st thou to me now? speak once again.
Soothsayer: Beware the ides of March.
Caesar: He is a dreamer; let us leave him: pass.”
(William Shakespeare, Julius Caesar)

Related words

BCE, calendar, calendar year, CE

Browse related words in the Macmillan Thesaurus.

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Liz Potter

Liz Potter

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