What exactly are the Ides of March?

Everyone knows we’re supposed to beware the Ides of March and may even remember they’re from William Shakespeare’s “Julius Caesar,” but what exactly do they mean?

Friends, Romans, Countrymen, lend me your knives

The Ides of March marked the day the Julius Caesar was assassinated by members of the Roman Senate in 44 B.C.E. A soothsayer, or psychic, warns Caesar to beware the day, but Caesar doesn’t heed him. He was then stabbed 23 times by about 60 conspirators, including his pal Marcus Brutus, as immortalized by Shakespeare’s “Et tu Brute?”

That particular line was likely exaggerated, but otherwise, the event as Shakespeare wrote it was lifted straight from historical accounts of the murder. Caesar, who had been named “dictator in perpetuity,” was really warned by a soothsayer, was cornered by the senators and killed before he could truly become a tyrant. Caesar’s death marked the end of the Roman Republic and the beginning of a civil war. It was a popular story even before Shakespeare’s 1599 play.

A date that will live in infamy

Ides comes from the ancient Roman calendar denoting the middle of the month, which in March is the fifteenth. (March also being the first month of the year in those days, until Caesar introduced the Julian calendar and moved the first of the year to January.) The Roman calendar was determined by the cycles of the moon — the middle of the month was when the full moon typically occurred.

Are “ides” singular or plural?

“Ides” are actually both, coming from the Latin “idus.” The word is plural when referring to the ides in every month, but singular when speaking of the middle of a particular month. It is unclear, however, why Shakespeare said the Ides “are” come rather than “is.” Perhaps his ghost will tell us.