ensure、insure、assure、guarantee、pledge与promise这些动词都有“保证”之意。
ensure : 侧重使人相信某个行为或力量产生的结果。
- The airline is taking steps to ensure safety on its aircraft.
航空公司正在采取措施以确保其航班的飞行安全。 - The role of the police is to ensure (that) the law is obeyed.
警察的职责就是确保法律得到遵守。
insure常与ensure换用，但前者多指经济方面的保证、保险。
- I'm not insured to drive his car.
我没有相关的保险，不能开他的车。 - The house is insured for two million dollars.
该房子投保了200万英镑。 - All our household goods are insured against accidental damage.
我们家里所有的物品都保了意外损失险。
assure : 侧重指消除某人思想上的怀疑或担心，从而有达到目的的保证感，但不如ensure普通。
- The unions assured the new owners of the workers' loyalty to the company.
工会向新企业主保证，工人们对公司是忠诚的。 - "Don't worry, your car will be ready tomorrow," the mechanic assured him.
“别担心，你的车明天就可以修好，”修理工向他保证。
guarantee : 指对事物的品质或人的行为及履行义务、义务等承担责任的保证。
- European Airlines guarantees its customers top-quality service.
欧洲航空公司保证为乘客提供最好的服务。 - The label on this bread says it is guaranteed free of/from preservatives (= it contains no preservatives).
这种面包的标签上写着保证不含防腐剂。
pledge : 正式用词，指通过郑重许诺、协议或立誓等保证承担某一义务或遵守某一原则。
- We are asking people to pledge their support for our campaign.
我们正请求人们承诺支持我们的运动。 - If you join the armed forces, you have to pledge allegiance to your country.
如果参军，你必须宣誓效忠你的祖国。
promise : 侧重表自己的主观意向，设法用语言使人感到稳当可靠。
- He promised faithfully to call me every week.
他信誓旦旦地保证每周都给我打电话。 - The government have promised that they'll reduce taxes.
政府已承诺要减税。
