I'm somewhat of a grammar Nazi, so it bugged me when I was reading a description of the Econ PhD program here at UMich:

This requirement is intended to insure that students are well versed in the particular research techniques that they will use in writing their dissertations. [emphasis mine]

I always thought there was a difference between the word "ensure" and the word "insure", in that "insure" was used strictly in the sense of guaranteeing something through insurance, while "ensure" is based on a method, or somebody's word. But I've seen these two words used in the same context by different sources. So the question is, is there a difference in the meanings of the two? Is "insure" the same as ensure, only with the added meaning tacked on?

I favor the use of "ensure" in my everyday writing. Then again, this doesn't say much because besides being strict about usage I'm also somewhat of a grammar contrarian: for example, I tend to use the 'se' form of the imperfect subjunctive tense in Spanish which, although functionally equivalent, is less common then the 'ra' form. But regarding the "ensure, insure" matter, the first result of a Google search seems to agree with me:

> > >to me "insure" means "to cover with
> > >insurance" while "ensure" means "to make damned sure of it."
> >
> > Second the motion.
> >
> > "Assure" has a different meaning altogether for me. "Assure," is a verb
> >meaning one person essentially consoles another. "I assure you the arm can
> >be reattached" is different than "I ensure you the arm can be reattached."
> 
> At the risk of a "Me too" posting, me too. I agree wholeheartedly on these
> three word meanings. None are synonomous with the others.

But Bartleby assures me that they are, for the most part, interchangeable.

Americans frequently prefer insure when it comes actually to writing or buying insurance policies, whereas both insure and ensure have the generic sense of making certain of outcomes, as in Our careful planning will insure [ensure] our success.

There are certain times when I regret being a prescriptive linguist. Mostly when I'm wrong.