The differences between insure, ensure, and assure doesn’t have to do with their definitions. In fact, their definitions are quite similar – each word means “to make sure of something.” Their differences involve the way they’re used in a sentence.
The general rules for these three words are:
- insure - to take out an insurance policy on an item
- ensure - to guarantee that something happens
- assure - to convince another person that something is true
As you can see, each word has a specific use connected to its definition. And using these words interchangeably would be both grammatically incorrect and confusing to the reader.
You buy insurance, which comes from the word insure, to protect yourself against financial risk. That's why most uses of insure relate specifically to finance or the insurance industry.
- John and Jodi needed to insure their home against flood damage.
- Insuring your home in anticipation of natural disasters is a good idea.
- Barbara got insured after she spoke to her local agent.
The word insure is often used in place of ensure when describing the act of protecting oneself (for example, “Learning martial arts insures that you can defend yourself”). While this use is technically correct by strict definition, it’s difficult to get exactly right, and both the AP stylebook and Chicago Manual of Style agree that ensure is almost always the better choice.
Keep insure for sentences about financial protection.
You ensure that something will happen by taking extra precautions. If you’re trying to say “make sure,” then ensure is the correct word to use.
Use ensure in the following ways:
- The dog owner always would ensure that he returned home quickly.
- Billy was to ensure that the computer was packed safely.
- He double-checked the stove to ensure it was off before leaving on vacation.
Unlike insure, ensure isn’t always about protecting yourself. It’s the most versatile word of these three commonly confused words.
When you’re trying to decide between insure, ensure, and assure, ensure is usually the right answer.
Just like insure and ensure, assure has the definition “to make sure” right in the word. However, assure is used when specifically talking about increasing someone’s confidence to make them more sure.
Consider the following examples:
- Suzanne assured Robby that his report to the board was excellent.
- Kelly was head over heels for Bill, but she did not feel assured that he felt the same way.
- I assure you, I didn’t cheat on the exam.
Of these three words, assure is the only one that always relates to a person. It’s not interchangeable with insure or ensure in this way, as those words don’t relate to a person’s feelings.
Assure makes another person feel sure, not the speaker.
If you’re stuck on which word to use, there are a few ways you can figure it out in the moment.
To help you remember when to use each word, keep the following hints in mind:
- You insure your car.
- You assure a person.
- You ensure everything else.
You can also put each word in its noun form to decipher which word sounds like the one you want.
- insurance - a policy that protects you financially
- ensurance - the act of ensuring (obsolete word)
- assurance - a statement to make someone feel confident
And finally, one more hint to tell these words apart: add the prefix re-.
- reinsure - to take out another insurance policy
- reensure - (not a word)
- reassure - to calm someone by convincing them that something is true
The differences between these words become much clearer when you put them into different forms. Remembering that insure is for money, assure is for people, and ensure is for actions is the most helpful way to ensure your vocabulary is correct.