A death sentence is a legal punishment that is given to someone who has been found guilty of committing a very serious crime, such as murder or terrorism. It means that the person will be executed, which is a painless way to die, usually by lethal injection. The purpose of this penalty is to serve as a deterrent and to remove dangerous individuals from society. In some countries, however, death sentences are not carried out, but instead replaced with life imprisonment or other forms of punishment.