Copy Editor’s Corner | Assure – Insure – Ensure
But while a dictionary may state that it’s okay to use insure in a context other than insurance, and assure to mean “guarantee,” many style guides have stricter guidelines.
AP style, for instance, assigns one meaning to each word:
“Use ensure to mean guarantee . . . insure for references to insurance . . . assure to mean to make sure or give confidence.”
This approach simplifies the matter and makes the definitions easier to memorize. While you could defend your usage by pointing to Merriam-Webster, style guides often trump dictionaries.
We consider the following a proper example of how to use insure:
Stan insures his car and his boat through the same company.
But we don’t love this sentence:
Peter makes his kids wear bike helmets to insure their safety.
We would have used ensure.
And this is a nice way to use assure:
I can assure you that the menu at La Belle Vie will not disappoint.