What's the noun for imprisonment? Here's the word you're looking for.
prison
A place or institution of confinement, especially of long-term confinement for those convicted of serious crimes or otherwise considered undesirable by the government.
(uncountable) Confinement in prison.
(colloquial) Any restrictive environment, such as a harsh academy or home.
“The order is taken to be a warrant committing the prisoner into custody for the Corrective Services Act.”
“A wartime prisoner, generally considered to be a prisoner of war, can be held indefinitely as long as the conflict lasts, but must be released as soon as the conflict ends.”
“The earl of Devonshire being interested in the blood of York, that was rather feared than nocent, remained prisoner in the Tower.”
“And within the Moliere canon, there aren't many hypocrites, misanthropes, suspicious husbands or would-be wife imprisoners that the Yorkshire-born Bedford hasn't sampled.”
“In addition, the untranslated memoirs of Jozef Juras and Alexander Barica tell astonishing tales of the paranoid and fanatical mentality of their imprisoners.”