Difference between Assure and Ensure

Key difference: The word, ‘assure’ is used as a promise. It is used to make somebody confident about something or to convince them of something. ‘Ensure’, on the other hand, is used to confirm or guarantee something. It makes sure that something will happen.

The words ‘assure’ and ‘ensure’ are commonly used interchangeably. This is mainly due to the fact that not only do the words look alike, sound alike and are even spelled alike, they actually originated from the same source. Both words ‘assure’ and ‘ensure’, in addition to ‘insure’ originated from the Latin securus, meaning ‘secure’. However, the words do actually have a difference meaning in context and are used at different instances.

The word, ‘assure’ is used as a promise. It is used to make somebody confident about something or to convince them of something. ‘Ensure’, on the other hand, is used to confirm or guarantee something. It makes sure that something will happen.

Dictionary.com defines ‘assure’ as:

To declare earnestly to; inform or tell positively; state with confidence to: She assured us that everything would turn out all right.
To cause to know surely; reassure: He assured himself that no one was left on the bus.
To pledge or promise; give surety of; guarantee: He was assured a job in the spring.
To make (a future event) sure; ensure: This contract assures the company's profit this month.
To secure or confirm; render safe or stable: to assure a person's position.
To give confidence to; encourage.

Dictionary.com defines ‘ensure’ as:

To secure or guarantee: This letter will ensure you a hearing.
To make sure or certain: measures to ensure the success of an undertaking.
To make secure or safe, as from harm.

Examples of ‘assure’:

I assure you the car is safe to drive.
She assured us that she had done what she promised.
I can assure you that the money will be paid.
I assure you that we will be on time.
He assured us that there were no delays.
In all of these markets, reform must assure transparency, prevent abuse, and protect the public interest.
Conversely, oil companies might sell futures contracts to assure a profit against future price drops.
John assured Mary that he'd come to the party early.
Let me assure you that I will be at the meeting at noon.
I assure you that I have been honest about the money I spent.

Examples of ‘ensure’:

The law ensures that you will have a fair hearing.
Ensure that you have plenty of gas in the tank before going on a long trip.
We need to ensure that she keeps her promise.
Winning the lottery ensured our happiness.
His loyalty will ensure your safety.
Hard work will ensure your success.
Senator Bordallo has been fighting to ensure that the people of Guam have a voice in Washington.
To ensure that as many Democrats as possible can cast their votes.
While we do not know all the details of this arrangement, the Fed must ensure that the plan protects the families that count on insurance.
To ensure there'd be enough food, Mary ordered twice as much food as last year.
To ensure my family’s safety, I have installed an alarm system.
Mauricio saved money from every paycheck to ensure he could buy gifts for his family at the end of the year.