Slavery began to exist before written history, in many cultures. A person could become enslaved from the time of their birth, capture, or purchase.
While slavery was institutionally recognized by most societies, it has now been outlawed in all recognized countries, the last being Mauritania in 2007. Nevertheless, there are an estimated 45.8 million people subject to some form of modern slavery worldwide. The most common form of the slave trade is now commonly referred to as human trafficking. Chattel slavery is also still practiced by the Islamic State of Iraq and the Levant. In other areas, slavery (or unfree labour) continues through practices such as debt bondage, the most widespread form of slavery today, serfdom, domestic servants kept in captivity, certain adoptions in which children are forced to work as slaves, child soldiers, and forced marriage.
The English word slave comes from Old French sclave, from the Medieval Latin sclavus, from the Byzantine Greek σκλάβος, which, in turn, comes from the ethnonym Slav, because in some early Medieval wars many Slavs were captured and enslaved. An older interpretation connected it to the Greek verb skyleúo 'to strip a slain enemy'.
There is a dispute among historians about whether terms such as "unfree labourer" or "enslaved person", rather than "slave", should be used when describing the victims of slavery. According to those proposing a change in terminology, "slave" perpetuates the crime of slavery in language, by reducing its victims to a nonhuman noun instead of, according to Andi Cumbo-Floyd, "carry them forward as people, not the property that they were". Other historians prefer "slave" because the term is familiar and shorter, or because it accurately reflects the inhumanity of slavery, with "person" implying a degree of autonomy that slavery does not allow for.
Indenture, otherwise known as bonded labour or debt bondage, is a form of unfree labour under which a person pledges himself or herself against a loan. The services required to repay the debt, and their duration, may be undefined. Debt bondage can be passed on from generation to generation, with children required to pay off their progenitors' debt. It is the most widespread form of slavery today. Debt bondage is most prevalent in South Asia.
Chattel slavery, also called traditional slavery, is so named because people are treated as the chattel (personal property) of the owner and are bought and sold as commodities. Typically, under the chattel slave system, slave status was imposed on children of the enslaved at birth. Although it dominated many different societies throughout human history, this form of slavery has been formally abolished and is very rare today. Even when it can be said to survive, it is not upheld by the legal system of any internationally recognized government.
Forced labour, or unfree labour, is sometimes used to refer to when an individual is forced to work against their own will, under threat of violence or other punishment, but the generic term unfree labour is also used to describe chattel slavery, as well as any other situation in which a person is obliged to work against their own will and a person's ability to work productively is under the complete control of another person. This may also include institutions not commonly classified as slavery, such as serfdom, conscription and penal labour. While some unfree labourers, such as serfs, have substantive, de jure legal or traditional rights, they also have no ability to terminate the arrangements under which they work, and are frequently subject to forms of coercion, violence, and restrictions on their activities and movement outside their place of work.