1. 警惕的，警觉的，注意的　 watchful and ready to deal with danger
2. 机灵的，敏捷的　 quick to see and act

　～ mind　反应敏捷的头脑
　～ movements　敏捷的动作
　～ mentally　思想上警惕
　～ in answering questions　留心回答问题
　～ to　随时注意
　～ to every sound and movement　对任何响动都很警觉

　He has an alert mind.　他很机灵。
　The alert listener will have noticed the error.　耳朵尖的人能听出这个错。
　He is a man alert in problem.　他是个留意问题的人。
　Our guerrillas suddenly became alert as the dogs barked.　狗叫了，我们的游击队员突然警觉起来。
　The rabbit seems to be very alert all its life.　兔子似乎一生都小心翼翼，十分警觉。
　Be alert for any sign of change in the patient.　对这个病人的病情变化要密切注意。
　The student is alert in answering the question.　这个学生回答问题小心谨慎。
　A monkey is very alert in its movements.　猴子的动作很敏捷。
　He is always alert to danger.　他对危险时刻保持警惕。
　She was alert to seizing an opportunity.　她机敏地抓住一个机遇。
　So alert she was that not a single error in the report slipped her.　她十分警觉，所以报告中没有一个错能逃过她的眼睛。

　vt.　使处于戒备状态；警告 make sb watchful and ready for possible danger

　～ the public　提醒公众
　～ amazingly　吃惊地警告
　～ cautiously　小心地警告
　～ extremely　完全地警告
　～ guardedly　谨慎地警告
　～ resolutely　绝对地警告
　～ sharply　尖锐地警告
　～ wisely　聪明地警告
　～ to the danger　提醒注意其危险性
　～ to the need　提醒注意其必要性

　The voice of the caller alerted her.　呼唤者的声音使她警觉起来。
　Sirens alerted the cities long before the enemy bombers arrived.　敌军轰炸机凌空以前，各城市早已鸣了警报。
　They alert the public to the need for pollution control.　他们提醒公众注意控制污染的必要性。
　He had phoned the nearby villages, alerting them to the possibility of forest fires.　他给附近几个村庄打了电话，叫人们注意森林可能起火。
　The guard was alerted by a man climbing towards him.　有一个人向卫兵爬过来，使卫兵警惕起来。

　The boss alerted the guard that thief might come out at night.　老板要警卫提防夜里可能有贼。
　The villagers alerted the traveller that wolves might come out in the night.　村民们叫旅行者提防，夜晚有狼群出没。

　The radio alerted coastal residents to prepare for the hurricane.　电台警告沿海居民做好预防飓风的准备。
　We will alert operating personnel to repair.　我们将通知操作人员去维修。

　There are hurricane warning systems for alerting island residents.　现在有了向岛上居民发出飓风警报的警报系统。

1. C S 警戒；戒备；警惕　a situation in which people are watching for danger and ready to deal with it
2. C 警报　a warning of danger or of a problem

　call an ～　发出警报
　sound the ～　拉响警报
　call off an ～　取消警戒状态
　go on ～　进入戒备
　24-hour ～　昼夜警戒
　active ～　战斗警报
　blue ～　空袭警报
　false ～　假警报
　full ～　全面戒备状态
　general ～　全面警戒
　No 1 ～　一级战备
　preliminary ～　预备警报
　red ～　紧急警报
　white ～　解除警报
　yellow ～　预备警报
　air ～　空袭警报
　ground ～　地面待战
　malfunction ～　故障报警
　nuclear ～　核警报
　during an ～　在警戒期间
　in state of ～　处于警戒状态
　the ～ against any possible aggression　警惕任何可能的侵略
　the ～ for any indications of battle　注意任何战事的迹象

　A national police alert was in effect.　全国警察实行戒备。
　The hurricane alert is over.　飓风警报解除了。
　The air-raid alert sounded at noon.　正午时响起了空袭警报。
　We'd just boarded the bus when the alert sounded.　我们刚登上公共汽车，警报就响了。
　If there is an alert, don't panic, just make your way to the exit.　如果有警报，不要惊慌，只要走向太平门就行了。
　The machine sounded the alert.　机器发出了警报。
　They received the alert at midnight.　他们在午夜接到警报。
　It's the alert signal.　这是警报信号。
　They were quiet during the alert.　警戒期间他们很安静。
　We should not run about aimlessly during an alert.　警戒期间不可到处乱跑。
　The whole country is in a state of alert.　全国正处于戒备状态。
　Security forces are on a high state of alert because of the President's visit.　由于总统来访，保安部门处于高度警戒状态。
　Sirens brought the whole street to the alert.　警报声使整条街道进入戒备状态。

 ♣ on alert
　警戒着，防备着　ready to take action to deal with a dangerous situation
　Place the troops on alert.　使部队处于戒备状态。
　The army was put on full alert as the peace talks began to fail.　当和平谈判开始失败时，军队处于高度戒备状态。
 ♣ on the alert
　密切注意着，随时准备着　paying attention to what is happening and ready to react quickly if necessary
　The troops were kept constantly on the alert.　部队奉命常备不懈。
　We were constantly on the alert against any surprise attack.　我们时时刻刻都在提防突然袭击。
　In the arctic, the seals that bask on the ice or swim in the water have to be continually on the alert against the Polar bear.　在北极区，海豹无论是在冰上晒太阳还是在水中游泳，都要时刻提防着北极熊。
　Be on the alert for pickpockets.　谨防扒手！
　Drivers must be on the alert for traffic signals.　驾驶员必须密切注意信号。
　The troops have been put on the alert for a possible enemy attack.　部队已处于警戒状态，以防敌军的进攻。
　We were warned to be on the alert for possible terrorist attacks.　我们接到随时提防恐怖分子袭击的警告。
　The police are on the alert for any suspicious packages that might contain bombs.　警察警惕着任何可能藏有炸弹的可疑包裹。
　She is often on the alert to avoid such company.　她时常警惕着，不和这样的人为伍。

 ♣ on alert, on the alert
　这两个短语形似义近，其区别是：on alert是针对危险情况的，意思是“防备着”;on the alert是针对事态发展的，意思是“随时准备着”。

　［同义词］ adj. active, aware, bright, careful, quick, watchful v. alarm, notify n. warning, siren
　［反义词］ adj. careless, inactive, slow, unaware
　［词源］意大利语all' erta（正监视着，正注意着）