n.警戒；警惕；【醫(yī)】失眠癥

In spite of vigilance a polar bear escaped from the zoo. 盡管警戒很嚴，北極熊還是逃出了動物園。

Police's vigilance was eventually rewarded. 警方時時警戒終有所獲。

We must maintain keen vigilance at all times. 任何時候我們都要保持高度的警惕。

過度警覺