永牢[eirou] life imprisonment
堅牢[kenrou] solid
入牢[nyuurou] imprisonment
牢屋[rouya] jail
破牢[harou] prison breaking

牢獄[rougoku] prison
土牢[tsuchirou] dungeon
水牢[mizurou] (punishment by being placed in a) water-filled chamber
牢固[rouko] firm
牢死[roushi] dying in prison