φυλακή

guard, watch, a watching, keeping watch, to keep watch, persons keeping watch, a guard, sentinels, of the place where captives are kept, a prison, of the time (of night) during which guard was kept, a watch i.e. a period of time during which part of the guard was on duty, and at the end of which others relieved them. As the earlier Greeks divided the night commonly into three parts, so, previous to the exile, the Israelites also had three watches in a night subsequently, however, after they became subject to the Romans, they adopted the Roman custom of dividing the night into four watches