alert

《柯林斯词典》（Collins Dictionary）对"alert"的解释：

形容词：

名词：

词语辨析：

形容词 "alert" 和 "vigilant" 都表示警觉的含义，但 "alert" 更强调对周围环境的快速反应和警觉性，而 "vigilant" 更强调警觉意识的持久性。

词汇扩充：

形容词 "alert" 可以衍生出名词 "alertness" 表示“警觉性”。

动词 "alert" 可以衍生出名词 "alerter" 表示“警报器”。

近义词：

反义词：

《牛津词典》（Oxford Dictionary）对"alert"的解释：

形容词：

名词：

用法：

"alert" 作为形容词时，可以修饰人或物，表示警觉、警惕、敏捷的状态。作为名词时，表示警报、警戒状态或警告。

例句：

1. The security guard was alert and noticed the suspicious activity.

这名保安警觉并注意到了可疑的活动。

2. The police issued an alert to warn the public about the escaped prisoner.

警方发布了一项警报，警告公众有逃犯在逃。

3. The dog barked loudly, alerting its owner to the presence of an intruder.

狗大声叫，提醒主人有人闯入。

4. The teacher asked the students to stay alert during the examination.

老师要求学生在考试期间保持警觉。

5. The hiker's alertness saved him from falling off the cliff.

这名徒步旅行者的警觉性使他免于跌落悬崖。

6. The security system is designed to detect any unauthorized access and raise an alert.

该安全系统旨在检测任何未经授权的访问并发出警报。

7. The government has issued a weather alert for the approaching storm.

政府发布了一则有关即将来临的风暴的天气警报。

8. The firefighters responded quickly to the alert and arrived at the burning building within minutes.

消防队员迅速响应警报，在几分钟内赶到了着火建筑物。

9. The child's cry of "help" put everyone on alert.

孩子的呼救声使每个人都警觉起来。

10. The security guard stayed alert throughout the night shift.

保安人员在整个夜班期间保持警觉。

11. The company issued a cyber security alert to all employees.

公司向所有员工发布了一条网络安全警报。

12. The lifeguard's alertness saved the swimmer from drowning.

救生员的警觉性使这位游泳者免于溺水。

13. The military is on high alert due to the increased threat of attack.

由于攻击威胁加大，军方处于高度戒备状态。

14. The driver's quick reflexes and alertness prevented a potential accident.

司机的快速反应和警觉性避免了一次潜在的事故。

15. The nurse remained alert for any changes in the patient's condition.

护士对患者情况的任何变化保持警觉。

16. The security cameras are constantly monitoring the premises for any alert.

安全摄像头不断监视着场所是否出现警报。

17. The police officer put out an alert for a stolen vehicle.

警察发布了一则关于被盗车辆的警报。

18. The company sent an email alert to all employees about the upcoming meeting.

公司向所有员工发送了一封关于即将举行的会议的电子邮件提醒。

19. The lifeguards are trained to be alert to signs of distress in swimmers.

救生员经过培训，对游泳者的苦恼迹象保持警觉。

20. The security guard sounded the alarm to alert everyone in the building.

保安人员按响警报，提醒大楼内的每个人。