Barbara of the Bonneville Power Administration in Vancouver, Washington, asked me to write about ensure, assure, and insure. I am happy to write from the U.S. perspective, and I am hoping my friends across the oceans and borders will enlighten us about any differences.
Here is an illustration with all three words:
I assure you that Morgan did ensure that the company will insure both vehicles.
Here are quick definitions based on my favorite U.S. style guides:
Ensure = make certain.
Insure = protect against financial loss.
Assure = promise, give confidence to.
The noun form of insure is insurance. Outside the insurance industry, some people use insure and ensure interchangeably, but careful writers don’t.
Let’s see if we agree which word goes in each blank:
Please _____ that this does not happen again.
You ought to _____ the painting for $24,000.
Please _____ Mrs. Rio that her coat will be delivered to her today.
How can I _____ that the package will arrive by tomorrow?
I _____ you that the figures are correct.
Before I give you my answers, remember my sample sentence with all three words? Please forget it. It would never be wise to use all three words in one sentence. Doing so would dizzy your readers rather than focusing them on your meaning.
Here are my answers for the blanks above: 1. ensure, 2. insure, 3. assure, 4. ensure, 5. assure.
Please let me know what works in Britain, Australia, Canada, and other lovely places.
P.S. If you like simple explanations of confusing word pairs, get my "60 Quick Word Fixes." It’s available as a PDF and booklet here.