A privateer was a privately owned vessel authorized by a government to attack enemy shipping under a commission, often called a letter of marque. In wartime, states used privateers to weaken rivals without paying for every ship themselves. A pirate, by contrast, committed robbery at sea without valid authorization, or acted outside the limits of a commission. The distinction depended on law and political recognition, not on whether the captured cargo was valuable or the attack was violent.
Privateering could blur into piracy. Commissions were issued for particular wars and targets; they did not grant unlimited permission to attack any ship. A raider who continued after peace, attacked neutral vessels, or exceeded lawful authority could be treated as a criminal. Captured ships might be brought before a court to decide whether the seizure was legitimate. In distant waters, enforcement was difficult, and rival governments could disagree over who counted as a lawful combatant.
The same sailor might work under a commission during wartime and face accusations of piracy in another context. That does not mean the categories were meaningless: legal documents and courts mattered to governments, merchants, and crews. It does mean that historical labels deserve scrutiny. When a source calls someone a pirate or privateer, consider who used the term, which authority stood behind it, and whether the relevant commission was valid at the time. Those details often explain the politics behind the accusation.