Assure vs Ensure vs Insure: Quick Explanation and Sentence Examples

These three verbs are indeed very close in meaning and even native English speakers tend to mix-up ensure and insure—though not often assure.

Assure is notably different from the other two because it usually means “to tell someone that something is certain or true”:

I assure you that the work will be done on time.

I assure you that we have lost the game. Sorry!

However, assure has a second meaning, which it shares with ensure and insure: “to guarantee” or “to make certain,”—as in, “to cause something to be a certain way,” or “cause something to surely happen”:

Please set your alarm clock to ensure that you get up in time for work.

I will insure that the invoices are added up properly.

Can we assure that the show will begin on time?

Nevertheless, these words are subtly different, even with this meaning illustrated above.

Assure emphasizes knowing that something is sure:

Correct: Please assure that the information on your application is correct.

Weird: A stray meteor assured the death of the dinosaurs.

The second sentence doesn’t work very well, because it doesn’t involve telling or knowing.

Ensure emphasizes safety or security, although it can still be used for negative things—as long as somebody wants to be sure of them.

Correct: Seat-belts almost ensure passenger safety.

Correct + ironic: Your mistake ensured that we would crash.

The second sentence is ironic because it implies that crashing is the kind of thing that one might try to ensure!

Insure can be used in these same ways; however, it emphasizes precautions and also has another meaning, referring to financial insurance:

Like ensure: Exercising insures that you will sleep well.

Financial insurance: I insured my musical instruments because they are delicate and rare.

And on that note, let’s mention that one can also have insurance in the more abstract sense of insure, and you can have assurance also, but not ensurance:

The new fence is not complete insurance against burglars.

We would like some assurance that you will not interfere with our plans.

However, ensurance is not a word! Ah, English.

More Examples of Using "Assure" in a Sentence

1. The serene landscape assured him that he had made the right decision.
2. Sandra assured me that she would be there on time.
3. I assure you that I am telling the truth.
4. I assure you that I am not angry, just disappointed.
5. Assure your boss that you will be on time for work.
6. I assured my parents that I would be safe while they were away.
7. Assuring the audience that they were safe, the fire marshal ordered everyone to leave the theater.
8. I am assuring you that everything is fine.
9. I am not confident enough to assure you of anything.
10. It's important to assure the customer that they are not alone in their frustration.

More Examples of Using "Ensure" in a Sentence

1. After ensuring that the test would not be completed soon, the professor took a lunch break.
2. To ensure that you get paid on time, please sign the required forms. 
3. Ensure that your resume is up-to-date.
4. To ensure that the product is as safe as possible, the company conducts numerous tests.
5. Ensuring that your pet is properly vaccinated is one way to help protect them from potentially deadly diseases.
6. By ensuring that you have a will in place, you can help make sure your loved ones are taken care of after you're gone.
7. It is important to ensure that any prescription medications are kept out of the reach of children.
8. To ensure a good night's sleep, be sure to avoid caffeine and alcohol before bedtime.
9. It is crucial to ensure that your car is in good working order before taking a long road trip.

More Examples of Using "Insure" in a Sentence

1. An insurance policy can help to insure that you are financially protected in the event of an unexpected accident or illness.
2. By insuring your car, you are protecting yourself from potential financial losses if it is damaged or stolen.
3. I always insure my car in the event of any damages that may occur during the year.
4. I want to make sure that our small business is insured against any losses that may occur.
5. The company's new plan is to insure all of its employees, even if they work part-time.
6. If we insure your equipment, then you're covered in case of an accident.
7. Insure your home and possessions with a solid insurance policy.
8. We as parents hope to insure our children against the risk of disease.
9. The most cost-effective way to insure your car is through the state's auto insurance program.
10. I'm going to insure my car for $20,000.