What is the difference between ‘assure’, ‘ensure’ and ‘insure’?

The verb ‘assure’ means to promise or guarantee something to someone. It is often used to convey confidence or certainty in a statement and to remove someone’s doubt about something. After the word ‘assure’, we usually have a person (assure you, assure him/her, assure them, etc.). Examples:

He assured me that he would be at the meeting on time.
I assure you that I have everything under control.
I assure you, the package will arrive by tomorrow.
I assure you, you will feel no pain.
I can assure you that the project will be completed on time.
My colleague assured me that I made the right decision.
She assured him (that) the car would be ready the next day.
The company assured investors of steady growth in the coming year.
The doctor assured the patient that the procedure would be painless.

The verb ‘ensure’ is used to indicate actions taken to make sure that something happens or is in a certain state. We cannot ensure a person; we use this verb with events and conditions. After the verb ‘ensure’ we often have ‘that’ + a fact. Examples:

Please ensure (that) all electronic devices are turned off during the flight.
Please ensure the meeting starts on time.
The new regulations are meant to ensure fair treatment for all employees.
We must ensure that the data is backed up regularly to prevent loss.
We must ensure that tourism develops in harmony with the environment.
We need to ensure that everyone has access to the meeting agenda.
You have a legal obligation to ensure that your child receives a proper education.

The verb ‘insure’ primarily refers to purchasing insurance for something, such as property or health. Examples:

All motorists are required, by law, to insure their cars.
I always insure my mobile phone against theft.
I insured my house against fire, flood damage and burglary.
I need to insure my new car against theft and accidents.
It is wise to insure your property against storm damage.
My house is insured for one million dollars.
What do you need to insure a car?
You need to insure your car before you can drive it.

Photo: New York Stock Exchange