The Greek storage jar Pandora opened is called a pithos. In Hesiod’s account, Pandora releases the troubles kept inside a large vessel, not a small modern box.
Pithoi were substantial ceramic storage containers used throughout the ancient Greek world. They could hold grain, oil, wine, or other supplies, and some were large enough to stand taller than a person. Their broad bodies and sturdy construction made them practical for long-term storage.
The familiar phrase “Pandora’s box” developed later. The Greek word pithos was translated into Latin as pyxis by Erasmus in the sixteenth century, and pyxis can mean a box or small container. That translation helped create the wording now common in English.
The myth itself does not establish a universally agreed archaeological design for Pandora’s vessel. Its important feature is that it contains evils or troubles released into the human world. “Pithos” is therefore the precise classical term, while “box” is the later conventional expression.