Nonperson

A nonperson is a citizen or a member of a group who lacks, loses, or is forcibly denied social or legal status, especially basic human rights, or who effectively ceases to have a record of their existence within a society ("damnatio memoriae"), from a point of view of traceability, documentation, or existence. The term also refers to people whose death is unverifiable.
Legal status.
Asserting that someone is a nonperson is implicitly a normative statement; by doing so, it is implied simultaneously that the person referred to is entitled to the rights that any person "should" have. Who is a person and what every person is entitled to depends on context and social norms. For example, wards that are under the authority of a legal guardian due to infancy, incapacity, or disability are not usually considered nonpersons.
Examples.
There are many possible meanings associated with the term "nonperson".
Prison camps.
In Nazi extermination camps, Jewish people and Romani were treated as nonpersons. The purpose of these camps was to systematically dehumanise these unwanted peoples, use them where possible, and dispose of them efficiently. "Nonperson" status was required because it removed the moral and social obstacles for committing otherwise objectionable acts of violence, crime, abuse, and murder.
Unofficially missing people.
Some people are covertly held by governments or other bodies, and effectively cease to exist. This happened under Pinochet's dictatorship in Chile and Argentina's last military dictatorship. It was also the guiding strategy behind the Nazi government's "Nacht und Nebel (Night & Fog)" policy in Western Europe. To dodge pointed questions regarding supposedly democratically controlled governments covertly holding people or employing torture, plausible deniability of knowledge might be used. The existence of ghost detainees in a secret CIA prison system is an example of this.
In North Korea even prominent people are "airbrushed from history", because the government has complete control over the internal media. For example Jang Song-thaek, the uncle of Leader Kim Jong-Un, has been removed from pictures and videos since his execution. KCNA and "Rodong Sinmun" began erasing references to Jang "as completely as possible", deleting some 100,000 and 20,000 news items from their websites, respectively.
To an extent, this is made both easier and harder by technology – easier because reliance upon technology is such that if a person's information is electronically deleted or was never stored in that manner they effectively cease to exist; harder because during every stage of a person's life from birth to death the accumulation of bureaucratic transactions makes it more and more likely that they will leave an official record somewhere.
Industrialized countries.
A person that does not appear on any official documents, is economically or socially inactive, or lives outside of what is defined as the "productive system" or "organized society" could be classified as a nonperson. This is often the case of homeless and marginalized people in general. Another example has been the group of The Erased in Slovenia, about 25,000 people, who lost their legal status and therefore all social, civil, and political rights after Slovenia declared its independence in 1991, because they did not register themselves in due time as "foreigners".
Also, some legally detained prisoners can be considered to be in a quasi-nonperson status, temporarily or indefinitely, to different extents depending on the reasons for and conditions of their detention. For example, in most countries, ordinary prisoners are denied political rights such as voting; in the most severe cases, total or partial isolation from the outside world can be inflicted.
Demonization.
A "nonperson" status can also be consciously or unconsciously applied to unwanted persons (demonization) by their surrounding society. This can be extended and applied to an entire nation or ethnic group, as often happens in wars or other conflicts.
This was the situation in the Nazi state with regard to Jews, and in most societies with regard to gypsies, and it is often applied in times of war to the entire enemy nation; its people are stripped of their "person status" and demonized, making them appear to be sub-human (not humans), and thus indirectly rationalizing any excess or abuse committed against them. Similar cases, concerning contra-revolutionaries, are found in most socialist states, where those demonized are often called "reactionaries".
It can be argued that the "nonperson" status, apart from the German deathcamps, can be found in its most literal form when considering certain prisoners of war, especially if they are or are considered to be illegal combatants.