A more thorough explanation:

Definition: In Roman law, a libellus supplex was a written petition, usually addressed to the emperor.

Example: A citizen of Rome who had a grievance or request would write a libellus supplex to the emperor, asking for redress or assistance.

Explanation: The libellus supplex was an important legal document in ancient Rome, as it was the primary means by which citizens could communicate with the emperor. All petitions had to be in writing, and the libellus supplex was the standard format for such requests. The example illustrates how a citizen might use a libellus supplex to seek help or justice from the emperor.