To direct the conversation into the area Skinned's talking about, the Walk Free Foundation uses this as their definition of slavery:
http://www.globalslaveryindex.org/terminology/Quote
TRAFFICKING IN PERSONS
Recruitment, transportation, transfer, harbouring or receipt of persons;
By means of threat or use of force or other forms of coercion, of abduction, of fraud, of deception, of the abuse of power or of a position of vulnerability or of the giving or receiving of payments or benefits to achieve the consent of a person having control over another person (these means are not required in the case of children);
With the intent of exploiting that person through:
Prostitution of others;
Sexual exploitation;
Forced labour;
Slavery (or similar practices);
Servitude; and
Removal of organs.
(UN Trafficking Protocol, 2000)
SLAVERY AND SLAVERY LIKE PRACTICES
The status or condition of a person over whom any or all of the powers attaching to the right of ownership are exercised. Includes slavery-like practices: debt bondage, forced or servile marriage, sale or exploitation of children (including in armed conflict) and descent-based slavery.
(The Slavery Convention (1926) and Supplementary Slavery Convention (1956))
FORCED LABOUR
All work or service which is exacted from any person under the menace of any penalty and for which the said person has not offered himself voluntarily.
(ILO Forced Labour Convention, 1930 (No. 29))
Underlying concepts
Walk Free Foundation’s (WFF) concept of modern slavery covers a number of terms defined in international law and legally in effect through national or state laws in many countries. The key concepts that we attempt to cover and measure are set out below.
Slavery
In law, slavery refers to situations where one person has such complete and absolute control over another person, that they really can treat that person as if they are a piece of property: able to be bought, sold, given away or disposed of.
Term defined in Article 1 1926 Slavery Convention.
Human trafficking
In law, human trafficking refers to three constituent elements:
The Act: Recruiting, transporting, transferring, harbouring or receiving a person; through
The Means: Threat or use of force, coercion, abduction, fraud, deception, abuse of power or vulnerability, or giving payments or benefits to a person in control of the victim; for
The Purpose: Exploitation which includes exploiting the prostitution of others, sexual exploitation, forced labour, slavery or
similar practices, and the removal of organs.
Where the victim is a child (under 18), there is no requirement of coercive means. It is sufficient if the child is both recruited, for example, and exploited through one of the recognized forms of exploitation (e.g.: slavery, organ removal, sexual exploitation, etc).
Term defined in Article 3 UN Trafficking Protocol.
Forced labour
In law, “forced labour” refers to work or service that is taken from a person under the menace of penalty and for which the person has not offered himself voluntarily. Excluded from this definition are compulsory military service, normal civil obligations, penalties imposed by a court action taken in an emergency, and minor communal services.
Term defined in Article 2 ILO Convention on Forced Labour
Debt bondage
In law, “debt bondage” refers to a worker pledging their labour, or the labour of others under their control as security for a debt; and either the real value of the work undertaken is never applied to paying off the debt, or the length and nature of the work that has to be undertaken to repay the debt is never properly limited or defined.
Forced or servile marriage
In law, “forced marriage” or “servile marriage” refers to situations where any person, without the right to refuse, is promised or given in marriage on payment of consideration to her family or guardian; or the spouse, family or clan of a person has the right to transfer her to another person for value received; or a person on death of their spouse is liable to be inherited by another.
Term defined in 1956 Slavery Convention, Article 1(c)
The situation of child marriage as forced marriage is not always clear cut. Where children are under the age of 16, it is very likely that any “marriage” is forced as children of this age are unlikely to be able to meaningfully consent to marriage. However, where the situation involves, for example, children who are 16 and 17, who marry with their own consent and the consent of their parents, this will not necessarily constitute forced marriage. But if consent of either child is not present, this would constitute forced marriage.
Sale or exploitation of children
In law, “sale or exploitation of children” refers to situations where children (under 18) are:
Transferred by one person to another for remuneration or other consideration; and/or
Used in sexual activities for remuneration or other consideration; and/or
Forcibly or compulsorily recruited for use in armed conflict.
Terms defined in Article 2 CRC Optional Protocol on Sale of Children, and Article 3 ILO Convention on Worst Forms of Child Labour.