The original Greek myth describes Pandora opening a jar, not a box. Hesiod uses the Greek word pithos, which referred to a large storage jar used for grain, wine, oil, or other goods.
The familiar expression “Pandora’s box” developed through a translation history. The Renaissance humanist Erasmus translated pithos into the Latin pyxis, meaning a box or small container, and that wording helped establish the image now used in English. The jar remained the more historically accurate object in relation to Hesiod’s account.
Ancient pithoi could be very large and were often stored upright. They were practical household containers, so the myth’s object was not necessarily a small decorative box. Modern paintings and illustrations commonly show a hinged box because of the later phrase.
This distinction is one of the best-known differences between the ancient source and popular culture. The “box” is traditional in modern language, but “jar” is the precise answer for the Greek story.