Statelessness means having no country that recognizes a person as a national. It is not usually caused by a single event, and it can pass from parents to children indefinitely.
Two systems for granting nationality
Countries generally confer citizenship by descent from a parent, by birth on the territory, or through some combination of the two.
Where a child is born in a country that grants nationality only by descent, to parents whose own country grants it only by birth on its territory, neither rule applies and the child may have no nationality.
This kind of gap is a byproduct of independently designed national laws rather than a decision by any government about that particular child.
How gaps open and close
Statelessness also arises from state succession, when borders change and new nationality laws leave some residents outside every new category.
Administrative causes are common as well: missing birth registration, destroyed records or an inability to prove a parent's status can leave a person unable to establish a nationality they may in principle hold.
Some legal systems have historically restricted the transmission of nationality by one parent, which has produced statelessness among children in particular family circumstances.
Documentation becomes the binding problem
Establishing nationality requires documents, and obtaining documents typically requires proving a status the applicant cannot demonstrate without them.
Birth registration is the usual foundation, and unregistered births create difficulties that persist across a life and pass to the next generation.
Where the family has crossed borders or fled conflict, obtaining records from the original jurisdiction may be impractical or unsafe.
What the absence of nationality means daily
Without recognized nationality, a person may be unable to obtain a passport, register a marriage, open a bank account, own property or work lawfully.
Access to schooling and health care varies by country, and some services are available in practice while remaining formally closed.
Because no state accepts the person as a national, deportation is often impossible as well, which can leave people in prolonged administrative limbo.
The frameworks that address it
International conventions address the status of stateless persons and the reduction of statelessness, but they bind only the states that have joined them and are implemented through domestic law.
Statelessness determination procedures exist in some countries and not others, and where none exists a person may have no route to have the status recognized at all.
Rules differ substantially between countries and change over time, so anyone facing a nationality question needs advice from an immigration attorney or a specialist organization in the relevant jurisdiction.