Parole is the provisional release of a prisoner who agrees to certain conditions. Originating from the Italian parole (voice, spoken words), the term became associated during the Middle Ages with the release of prisoners who gave their word of honor to abide by certain restrictions. Both civilian prisoners and prisoners of war may be paroled under certain circumstances. Parole should not be confused with probation, which is a term of supervision assigned instead of a prison sentence rather than early release from prison. In criminal justice systems, parole is the supervised release of a prisoner before the completion of their sentence in prison. This differs from amnesty or commutation of sentence in that parolees are still considered to be serving their sentences, and may be returned to prison if they violate the conditions of their parole. A specific type of parole is medical parole or compassionate release which is the release of prisoners on medical or humanitarian grounds.