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vigilance; caution; alertness; precaution; being on guard
台風接近に伴い、気象庁が警戒を呼びかけた。
As the typhoon approached, the Japan Meteorological Agency urged people to stay alert.
周囲の動きに警戒しながら、慎重に進みました。
I proceeded cautiously, remaining vigilant of the movements around me.
不審者に対して警戒心を持つことが大切です。
Stay alert to suspicious people around you.