Alea iacta est ("The die is cast") is a variation of a Latin phrase (iacta alea est ) attributed by Suetonius to Julius Caesar on 10January 49 BC, as he led his army across the Rubicon river in Northern Italy, in defiance of the Roman Senate and beginning a long civil war against Pompey and the Optimates. The phrase is often used to indicate events that have passed a point of no return. The phrase was a quote from a play by Menander, and according to Plutarch, Caesar originally said the line in Greek rather than Latin. The Latin version is now most commonly cited with the word order changed (Alea iacta est), and it is used both in this form, and in translation in many languages. The same event inspired another related idiom, "crossing the Rubicon".

Meaning and forms

Caesar was said to have borrowed the phrase from Menander, the famous Greek writer of comedies, whom he considered a great playwright. The phrase appears in the lost play Arrephoros, as quoted in Deipnosophistae. Plutarch reports that these words were said in Greek: Appian, also writing in Greek, reports a very similar phrase: Suetonius, a contemporary of Plutarch and Appian, writing in Latin, has the quote in Latin instead of Greek: Lewis and Short, citing Casaubon and Ruhnk, suggest that the text of Suetonius should read iacta alea esto (reading the third-person singular future imperative esto instead of the present one est), which they translate as "Let the die be cast!", or "Let the game be ventured!". This matches Plutarch's use of third-person singular perfect middle/passive imperative of the verb ἀναρρίπτω, i.e. ἀνερρίφθω κύβος (anerrhī́phthō kýbos, ). In Latin alea refers to a game with dice and, more generally, a game of hazard or chance. Dice were common in Roman times and were usually cast three at a time. There were two kinds. The six-sided dice were known in Latin as tesserae and the four-sided ones (rounded at each end) were known as tali. In Greek a die was κύβος kybos.