assure, ensure, insure, guarantee都含有一定的"保证"之意
assure 表示向某人保证某事一定会发生(内含有让某人放心之意,以消除疑虑) assure sb. of sth /assure sb. that…
He assured us of his ability to solve the problem.他向我们保证他有能力解决这个问题。
The witness assured the judge that he was telling the truth .
ensure “确定,保证” 确保某种行为一定会发生 ensure sth. /ensure that…
I will ensure that the car arrives by six o’clock.
我保证汽车六点钟以前到。
This medicine will ensure you a good night’s sleep.
这药能保证你睡一夜好觉。
insure 意思是为防不测向保险公司付钱投保
My house is insured against fire.我的房子保了火险。
guarantee 对某事物的品质或人的行为"提出担保",对事物、商品等无质量,性能等方面的欺诈行为做出保证
The cooker is guaranteed for five years. 本炊具保用五年。
Can you guarantee me a job when I get there?
你可以确保我到那儿就可以找到一份工作吗?