Solitary confinement (also shortened to solitary) is a form of imprisonment in which an incarcerated person lives in a single cell with little or no contact with other people. It is a punitive tool used within the prison system to discipline or separate incarcerated individuals who are considered to be security risks to other incarcerated individuals or prison staff, as well as those who violate facility rules or are deemed disruptive. However, it can also be used as protective custody for incarcerated individuals whose safety is threatened by other prisoners. This is employed to separate them from the general prison population and prevent injury or death.
A robust body of research has shown that solitary confinement has profound negative psychological, physical, and neurological effects on those who experience it, often lasting well beyond one's time in solitary. While corrections officials have stated that solitary confinement is a necessary tool for maintaining the safety and security of prisons and jails, numerous medical, mental health, and legal professional organizations have criticized the practice and hold the view that it should be sharply curtailed. Due to the negative connotation around the term "solitary confinement", alternative terms are now used interchangeably: administrative segregation, restrictive housing, and close management (level 1).