n.警戒；警惕；【医】失眠症
In spite of vigilance a polar bear escaped from the zoo. 尽管警戒很严，北极熊还是逃出了动物园。
Police's vigilance was eventually rewarded. 警方时时警戒终有所获。
We must maintain keen vigilance at all times. 任何时候我们都要保持高度的警惕。
过度警觉
