What’s The Difference Between “Assure,” “Ensure,” And “Insure”?

In the middle of a thorny situation you might find yourself wanting to comfort someone and reaffirm that everything will be OK. But should you assure them that all is well or ensure them? And what about insure, how does it fit in with the other two?

Assure, ensure, and insure ultimately derive from the Latin word sēcūrus meaning “safe.” As with many words that share ancestors, these terms’ meanings can overlap and in some cases, they may function as synonyms. In fact, ensure and insure have a very close history: the words functioned as two spelling variants of the same term for hundreds of years. Essentially, they were the same word!

So what’s the discerning word lover to do? Well, for one thing, we can focus on several ways assure, ensure, and insure are used distinctly today. We assure you it’s not as painful as it sounds!

What does assure mean?

Assure was the first of the three to enter English with a reflexive sense of “to have confidence, trust, rely.” Today, the term is most commonly used to mean “to state with confidence to” or “to cause to know surely,” conveying the action of putting someone’s mind at ease, as in She assured us that everything would turn out all right.

What does ensure mean?

Ensure entered English shortly after assure with the meaning “to declare earnestly to; state with confidence to.” Today it is widely used to convey the action of securing or guaranteeing an outcome or development, as in This letter will ensure you a hearing.

What does insure mean?

As we’ve mentioned, insure entered English as a variant of ensure. However, in the mid-1600s, insure picked up a financial sense of “to pay a sum to secure indemnity to or on, in case of loss, damage, or death.” This financial sense is what distinguishes it today.

Nowadays, we primarily use insure to talk about providing or obtaining insurance, as in After all his car accidents, the company refuses to insure him again. Insure can be used to talk about other kinds of risk, but in that usage, the term is typically followed by the word against, as in We insured against disappointment by making an early reservation.

How to use assure, ensure, and insure

As you can see, all of these terms address the action of making certain or guaranteeing, but each in a slightly different way. The most important distinction to remember when trying to decide which to use is that insure is the only of the three that explicitly refers to insurance policies and financial risk. The following examples will help clarify its use:


  • Before you drive that car, you know you have to insure it, right?
  • It cost Armando a lot of money to insure his old house.

To assure is to “declare earnestly” or with confidence, similar to reassure, a word that appears as a synonym for assure. To ensure is related to the outcome of a situation. For example:


  • The teacher assured the students that they were prepared for the test.
  • Can you assure us that we have enough vaccines for everyone?
  • The team needs to practice as much as it can to ensure a decisive victory Saturday.
  • With a budget that small, we can’t ensure success in this marketing campaign.