Notes on English usage - insure, ensure, assure
These words cause confusion, partly because there are differences between British and American usage.
In British usage their meanings are quite distinct, namely:
insure - to protect something (your house, car, etc) against loss or damage, usually by taking out an insurance policy.
ensure - to make sure that something will happen, as in "we need to ensure that she keeps her promise".
assure - to make somebody confident about something or to convince them, as in "I can assure you that the money will be paid" or "She assured us that she had done what she promised".
In American usage, insure and ensure have, for many people, simply become variant spellings of each other and the distinction in meaning has been lost. However, I am told that this is not the case universally.
Remember that we use "ensure" to refer to future possibilties and "assure" when something is already in place or has happened.
There is also confusion over "insurance" and "assurance", in that we typically have "car insurance" but "life assurance". The thing to remember here is that we insure against possibilities but assure against the consequences of certainties - your car MAY be damaged or stolen, but your life will DEFINITELY come to an end one day - sorry!