Ensure vs. Insure
While many sources state that ensure and insure can be used interchangeably, I disagree. I concur with the Chicago Manual of Style, (quoted at JSU):
assure/ensure/insure – “Ensure is the general term meaning to make sure that something will (or won’t) happen. In best usage, insure is reserved for underwriting financial risk. So we ensure that we can get time off for a vacation, and insure our car against an accident on the trip. We ensure events and insure things. But we assure people that their concerns are being addressed.” (Chicago, 213)
In two recent books, The Omnivore’s Dilemma and Three Cups of Tea, the authors and editors have used “insure” to mean “make certain will happen.” I think ensure better captures this meaning:
I assure you, gentle reader, I wish publishers would ensure the accuracy of their text by consulting the Chicago Manual of Style, since insuring something implies that a policy has been paid for.