1. Capture in War: One of the primary sources of slaves in ancient Greece was capturing individuals during wars and military conflicts. When Greek city-states or armies went on campaigns, they often took captives who could be sold into slavery.
2. Barbarian Origins: The Greeks often considered non-Greek people as barbarians, and it was common for non-Greek individuals to be enslaved. Many slaves came from neighboring regions like Thrace, Scythia, and Asia Minor.
3. Piratical Raids: Piracy was prevalent in the Mediterranean Sea, and pirates would raid ships and coastal areas, capturing people whom they would then sell into slavery.
4. Debt Bondage: In certain cases, individuals who were unable to repay debts could become enslaved as a form of payment.
5. Orphanhood: Orphans or abandoned children might end up in slavery, especially if they had no relatives or guardians to take care of them.
6. Self-Sale: In rare instances, individuals might choose to sell themselves into slavery voluntarily, usually to escape poverty or for financial reasons.
7. Kidnapping: Slave traders and individuals involved in the slave trade would sometimes resort to kidnapping free people to sell as slaves.
It is important to note that slavery and the treatment of slaves varied across different Greek city-states, and certain policies and legal protections emerged over time to regulate slavery and improve the conditions for slaves.