What is Manumission?

Legal Definition
Manumission, from manumit /ˌmænjəˈmɪt/, is the act of a slave owner freeing his or her slaves. Different approaches developed, each specific to the time and place of a society's slave system.

The motivations of slave owners in manumitting slaves were complex and varied. Firstly, manumission may present itself as a sentimental and benevolent gesture. One typical scenario was the freeing in the master's will of a devoted servant after long years of service. A trusted bailiff might be manumitted as a gesture of gratitude; for those working as agricultural laborers or in workshops, there was little likelihood of being so noticed.

Such feelings of benevolence may have been of value to slave owners themselves as it allowed them to focus on a "humane component" in the human traffic of slavery. In general, it was more common for older slaves to be given freedom, once they had reached the age where they were beginning to be less useful. Legislation under the early Roman Empire put limits on the number of slaves that could be freed in wills (Fufio-Caninian law 2 BC), which suggests that it had been widely used.

Freeing slaves could serve the pragmatic interests of the owner. The prospect of manumission worked as an incentive for slaves to be industrious and compliant. Roman slaves were paid a wage (pecunium) with which they could save up to, in effect, buy themselves. Manumission contracts found in some abundance at Delphi specify in detail the prerequisites for liberation.

Manumission was not always charitable or altruistic. In one of the stories in the Arabian Nights, in the Sir Richard Francis Burton translation, a slave owner threatens to free his slave for lying to him. The slave says, "thou shall not manumit me, for I have no handicraft whereby to gain my living."
-- Wikipedia
Legal Definition
Contracts. The agreement by which the owner or master of a slave sets him free and at liberty; the written instrument which contains this agreement is also called a manumission.

2. In the civil law it was different from emancipation, which, properly speaking, was applied to the liberation of children from paternal power. Inst. liv. 1, t. 5 & 12; Co. Litt. 137, a; Dane's Ab. h. t.
-- Bouviers Law Dictionary
Legal Definition
The act of liberating a slave from bondage and giving him freedom. In a wider sense, releasing or delivering one person from the power or control of another. See Fenwick v. Chapman, 9 Pet. 472, 9 L. Ed. 193; State v. Prall, 1 N. J. Law, 4.
-- Black's Law Dictionary
Legal Definition
The giving of liberty to one who has been in just servitude, with the power of acting, except as restrained by law. See 9 Pet. (U. S.) 461, 9 L. Ed. 193.
-- Ballentine's Law Dictionary