• Abduction – The act of taking someone away by force, fraud or persuasion.
• Absconding – The action by which a person intentionally seeks to avoid specific ongoing legal proceedings, of which the person has been notified, or their outcome by not surrendering to the custody of a court or by not remaining available to other competent authorities.
• Acceptance and Approval – The international act so named whereby a State establishes on the international plane its consent to be bound by a treaty
• Accession – The international act so named whereby a State establishes on the international plane its consent to be bound by a treaty.
• Adoption – The statutory process of terminating a child’s legal rights and duties toward the natural parents and substituting similar rights and duties toward adoptive parents.
• Agreement (International) – The merger of wills of two or more international subjects for the purpose of regulating their interests by international rules.
• A refugee – is a person who has fled their own country because they are at risk of serious human rights violations and persecution there. The risks to their safety and life were so great that they felt they had no choice but to leave and seek safety outside their country because their own government cannot or will not protect them from those dangers. Refugees have a right to international protection.
• An Asylum-Seeker – is a person who has left their country and is seeking protection from persecution and serious human rights violations in another country, but who hasn’t yet been legally recognized as a refugee and is waiting to receive a decision on their asylum claim. Seeking asylum is a human right. This means everyone should be allowed to enter another country to seek asylum.
• Bail – An alternative to detention consisting in the deposit of a sum of money to guarantee an individual’s future compliance with immigration procedures, including appearing at future hearings or compliance with a deportation order. The sum of money is returned if the individual appears, or it is otherwise forfeited. 
• Country of Origin – The country that is a source of migratory flows (regular or irregular).
• Emigration – The act of departing or exiting from one state with a view to settling in another
• Forced Displacement – The UNHCR defines "displaced "as a result of persecution, conflict, generalized violence or human rights violations.
• Freedom of Movement – a human right comprising three basic elements: freedom of movement within the territory of a country, the right to leave any country and the right to return to his or her own country.
• Human Trafficking – is the recruitment, transportation, transfer, harbouring or receipt of people through force, fraud or deception, with the aim of exploiting them for profit. Men, women and children of all ages and from all backgrounds can become victims of this crime, which occurs in every region of the world. The traffickers often use violence or fraudulent employment agencies and fake promises of education and job opportunities to trick and coerce their victims.
• Immigration – a process by which non-nationals move into a country for the purpose of settlement.
• Irregular Migration – This is the movement of persons that takes place outside the regulatory norms of the sending, transit and receiving countries. There is no clear or universally accepted definition of irregular migration. From the perspective of destination countries it is entry, stay or work in a country without the necessary authorization or documents required under immigration regulations. From the perspective of the sending country, the irregularity is seen, for example, in cases in which a person crosses an international border without a valid passport or travel document or does not fulfil the administrative requirements for leaving the country. There is, however, a tendency to restrict the use of the term “illegal migration” to cases of smuggling of migrants and trafficking in persons. It is also preferred to use the term irregular migrant or undocumented migrant to describe a migrant without the appropriate permission to reside.
• Labour Migration – The movement of persons from one state to another, or within their own country of residence, for the purpose of employment. Labour migration is addressed by most states in their migration laws. In addition, some states take an active role in regulating outward labour migration and seeking opportunities for their nationals abroad.
• Migrant – The International Organization for Migration defines a migrant as any person who is moving or has moved across an international border or within a state away from her/his habitual place of residence, regardless of (1) the person’s legal status; (2) whether the movement is voluntary or involuntary; (3) what the causes for the movement are; or (4) what the length of the stay is.
• Migrant Flow (International) – The number of international migrants arriving in a country (immigrants) or the number of international migrants departing from a country (emigrants) over the course of a specific period.
• Migrant Worker – A person who is to be engaged, is engaged or has been engaged in a remunerated activity in a State of which he or she is not a national.
• Migration – The movement of a person or a group of persons, either across an international border or within a state. It is a population movement encompassing any kind of movement of people, whatever its length, composition and causes. It includes the migration of refugees, displaced persons, economic migrants and persons moving for other purposes, including family reunification.
• Migrant Smuggling – is the facilitation, for financial or other material gain, of irregular entry into a country where the migrant is not a national or resident. The criminals behind this highly profitable business seize the opportunity created by the need or desire of people to escape not just poverty and lack of employment opportunities but also natural disaster, conflict or persecution.
• Receiving country – The country of destination or a third country. In the case of return or repatriation, the receiving country is also the country of origin. It is also a country that has accepted to receive a certain number of refugees and migrants on a yearly basis by presidential, ministerial or parliamentary decision.