Many differences exist between the terms assure, ensure and insure.
The term assure is a verb of confirmation. It means to confirm something in another person’s mind or to drive a point home. One could also use it to emphatically emphasize an idea or comment. For example, “I assure you that I do not smoke cigarettes!” is a strong confirmation that the person does not smoke cigarettes. The term is best used when the writer wants to state and restate something so that there will be no mistakes about it.
The term ensure is a verb that means to make sure that some action is either carried out or is going to occur. One should use the term ensure when he or she is trying to evoke confidence or security in another party. For example, “Please ensure that the doors to the office are locked when you are counting the safe” is a request for the person to make certain that something happens.“Our company ensures that you will be 100 percent happy with our product” almost sounds as if it is a promise. The company is trying to comfort and reassure its customers of their impending satisfaction.
Insure is a term that means to protect or safeguard something. People most commonly use it when they are referring to health, life or automobile policies. Examples of this term in action are as follows:
“Are you going to insure the car?”
“Did you insure your home before you bought it?”
“Will they insure a person who has a terminal illness?”