a.

1. 警覺的；警惕的；留神的[（+to）]
   She is alert to every sound and movement.

   她對每一個聲音和動作都很警覺。

2. 機敏的，靈活的[（+in）]
   The boy was alert in answering the stranger's questions.

   男孩很機敏地回答了陌生人的問題。

n.[C]

1. 警戒，警報
2. 警戒狀態；警戒期間
   She was always on the alert for some new calamities.

   她總是保持警覺以防某種新的災難。

vt.

1. 向……報警；使警覺；使注意[（+to）]
   The doctor alerted me to the danger of a heart attack.

   醫生提醒我注意心臟病發作的危險。

2. 通知（軍隊，船隻等）待命；通知[（+for/about）][O2]
   She's alerted me for weekend duty.

   她已通知我週末值班。

adj.

n.

1. the state of being alert:
   everyone should be on the alert for terrorists.
2. a warning of danger.
3. a prompt or similar signal on an electronic device.

v.