watchful: is the least explicit term: played under the ~ eyes of their mothers.    在母亲警觉的双眼下玩耍


vigilant: suggests intense, unremitting, wary watchfulness: ~ taxpayers forestalled all attempts to raise taxes.    （wary也有警觉的意思，但强调怀疑和警惕风险be suspicious and on the look-out for dangers，如be wary of strangers who offer you a ride提防那些主动让你搭车的陌生人，如the cat eyed him warily[url=][/url]那只猫警惕地注视着他）


wide-awake: stresses keen awareness of and watchfulness for opportunities and developments more often than for dangers: ~ observers will recall other summit meetings.


alert: stresses readiness or promptness in meeting a problem or a danger or in seizing an opportunity: ~ traders anticipated the stock market's slide.   （红色警戒red alert是一款游戏, U.S. military on 'high alert' in the Persian Gulf nations of Bahrain and Qatar美军在波斯湾巴林卡塔尔提升战备，都有时刻准备警惕的意思）


watchful警觉: 泛指对危险机遇的警觉，不明确，vigilant警惕: 表示密切不停歇的警觉，wide-awake清醒精明: 多用于机会发展，而非危险，alert警惕警戒: 强调时刻准备处置问题危险或抓住机遇。    


记忆方法: 1）首字母WVWA想成A WVW很像一个波浪，想成风波<==引人警觉


         2）警觉的意思是关注及时察觉危险或机遇mean being on the look-out especially for danger or opportunity.   (look-out"向外看"形容警觉关注的样子，如we should keep a sharp look-out for their disruptive activities我们要严防他们的破坏活动 ; be on the look-out==be on the watch)