Ensure vs. Insure are homophones and easily confused words. Just to add to the confusion, their meanings are nearly identical. I think this is one of those situations where most common usage makes a big difference.
The spell-check application in most word processing software programs would not catch a slip-up among these three words. As long as it’s a word, and it is spelled correctly, spell-check keeps on scanning the document for more obvious word mistakes.
Ensure is a verb. It means guaranteeing results: security, safety, freedom from risk. It means to make sure of something. It relates to feeling secure, or doing what it takes to instill confidence in what you do and provide peace of mind when someone places their trust in you or what you do for them.
Insure is a verb. Its related noun, insurance, means a program a property owner pays for to receive financial reimbursement in case of damage or theft to their own property or someone else’s property. So to insure is what the insurance company is doing when they take someone on as a client. In the case of health insurance, programs co-pays for people to receive preventive care and treatment for ailments. Life insurance meanwhile, is a program that pays the surviving family members in case of their provider’s death.
The following sentence uses both words correctly:
It’s considered financially responsible to insure yourself and your property, but it also ensures peace of mind should a crisis occur.