Immurement, also called immuration or live entombment, is a form of imprisonment, usually until death, in which someone is placed within an enclosed space without exits. This includes instances where people have been enclosed in extremely tight confinement, such as within a coffin. When used as a means of execution, the prisoner is simply left to die from starvation or dehydration. This form of execution is distinct from being buried alive, in which the victim typically dies of asphyxiation. By contrast, immurement has also occasionally been used as an early form of life imprisonment, in which cases the victims were regularly fed and given water. There have been a few cases in which people have survived for months or years after being walled up, as well as some people, such as anchorites, who have volunteered to be immured.