Slavery, a system under which an individual is held as the property of another to be used or disposed of at the will of the owner, or master. Slavery has existed throughout most of human history and is still practiced in some parts of the world. It originated in prehistoric times, when it was found to be more profitable to enslave than to slaughter captives of war. The term “slave" dates from the Middle Ages, when it came into common usage in Europe because of the large numbers of Slavs who had been forced into servitude.

Warfare was the original source of slave labor. When slavery proved economically advantageous, it was extended to include debtors and criminals. To insure a continuous and plentiful supply of slaves, a slave trade was established, with people being seized and sold into slavery. Children born of slaves were also enslaved.

The status of slaves and their treatment varied greatly in different times and places. In some societies, slaves were considered merely chattels, pieces of property. They had no rights; their lives and labors belonged to their owners. In other social systems, slaves were recognized as human beings. Thus they received certain protections under the law, and manumission (release from slavery) was sometimes possible.

Slaves were utilized in agriculture, industry, commerce, domestic service, and the armed forces. The conditions of their labor ranged from the highly privileged position held by the well-educated teacher slaves of Rome to the miserable existence of those who worked in the mines.

Throughout history various legal, social, economic, and philosophical arguments—typically involving prejudices of race, color, nationality, or religion—were made to justify slavery. The view that enslavement was an inherent moral evil was not forcefully propounded until an antislavery movement began to develop late in the 18th century.