On occasion we’ve looked at troublesome twins like “imply” and “infer,” but what about triplets?

In a doctor’s office recently, I spotted a small gadget on the wall with a cautionary message: “Please assure proper disposal.” (The gadget lifted like a mailbox and must have been a safe place for disposing used needles.) Was “assure” correct, or should that have been “ensure” or “insure”?

Test your assuredness with this quick quiz. Select the right word.

1. To (assure/ensure/insure) that we submit the proposal on time, let’s aim to mail it a week early.

2. Can you (assure/ensure/insure) me that everyone will know I’m only joking?

3. This bubble wrap (assures/ensures/insures) that none of the plates will be harmed in shipping.

4. To (assure/ensure/insure) against any misunderstanding of our new procedure, we will discuss every aspect of it at the next team meeting.

5. I wore two sweaters to the game to (assure/ensure/insure) that I’d be warm enough in the upper deck.

The distinctions and answers

The object of “assure” is nearly always a person or people. I assure you. She assured them. The doctor assured her patient. So “assure” is correct in #2.

“Ensure” means “make sure.” So although we might have learned the other two first as we were developing our vocabulary as youngsters, “ensure” is the one we probably use the most in workplace communications. Quite often in our messaging we are making sure (ensuring). “Ensure” is correct in #1, #3, and #5.

We use “insure” when we are literally referring to insurance (insuring our home or car) or when we are simulating taking out an insurance policy and using the phrase “insure against.” So the discussion at the meeting in #4 was an action to insure against being misunderstood.

Note that when we mean actual insurance the usual preposition after “insure” is “for.” (The horse was insured for $1 million.)

Where I’m not sure myself

Full disclosure: I have trouble with the phrase “ensuring/insuring the future.” Take this example: By protecting our environment, we are ensuring/insuring our future. Are we making sure (ensuring) that we have a future, or is protecting our environment like taking out an insurance policy (insuring)?

For this reason I deploy my escape hatch (often a wise move when we’re unsure of what’s correct) and just use other words to try to make the same point. In some cases “safeguard the future” works; in other instances I like “brighten the future.”

If you have the solution, please let me know.


So the gadget message should have been “Please ensure proper disposal.”

In addition to presenting workshops on writing in the workplace, Norm Friedman is a writer, editor, and writing coach. His 100+ Instant Writing Tips is a brief “non-textbook” to help individuals overcome common writing errors and write with more finesse and impact. Learn more at

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