When do I use “insure” and when do I use “ensure”? I can never remember which is which.

Well, there’s a pretty good reason that you find them confusing. Technically, they started out as just variant spellings of one another, so they meant the same thing. And some sources will tell you that insure can still mean to make certain of something, especially by taking precautions.

But generally, nowadays, your safest bet is to use insure only if money has changed hands and complicated policies have been signed. Ensure is for any other situation, when you’re making sure of something but not contracting with someone to pay you if things go wrong.

If you’re looking for a mnemonic, try thinking that ensure is for “make sure,” which has two E’s but no I’s, and insure is for when there’s a policy.