Slavery is, in the strictest sense of the term, any system in which principles of property law are applied to people, allowing individuals to own, buy and sell other individuals, as a de jure form of property. A slave is unable to withdraw unilaterally from such an arrangement and works without remuneration. Many scholars now use the term chattel slavery to refer to this specific sense of legalised, de jure slavery. In a broader sense, however, the word slavery may also refer to any situation in which an individual is de facto forced to work against his or her will. Scholars also use the more generic terms such as unfree labour or forced labour, to refer to such situations. However, and especially under slavery in broader senses of the word, slaves may have some rights and protections according to laws or customs.
Slavery began to exist before written history, in many cultures. A person could become a slave 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 still more slaves today than at any previous point in history: an estimated 45 million people remain enslaved 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, serfdom, domestic servants kept in captivity, certain adoptions in which children are forced to work as slaves, child soldiers, and forced marriage.