If you assure someone that something is true, you tell them it is definitely true, especially when they are worried or doubt that it is true. You can also assure someone of something, for example, a fact, your sincerity, or the importance of something.

1. He had been able to assure them that the schools would not close.
2. You’re wearing a wig. – I can assure you I’m not!
3. A top official summoned some Americans to his office to assure them of their safety.

If you ensure that something happens, you do what is necessary to make it happen. Note that in American English, ensure can also be spelled insure.

4. The accounts department will ensure that your tax is paid.
5. Eating these foods ensures that they get enough vitamin C.
6. He would do whatever was necessary to ensure victory.

In British and American English, insure is normally used to talk about protecting against risks. If you insure your property, you pay money to an insurance company that agrees to pay money to you if your property is lost, damaged, or stolen. You can also insure yourself.

7. Insure your baggage before you leave home.
8. If you bring your bicycle you must have it insured against theft.
9. He insured himself against all eventualities.