When I should use “assure” vs. “ensure” vs. “insure”?

Question

When is it appropriate to use assure vs. ensure vs. insure?

Answer 1

Assure: promise, as in I assure you the car is safe to drive.

Ensure: confirm, as in Ensure that you have plenty of gas in the tank before going on a long trip.

Insure: protect with an insurance policy, as in Insure the car before your trip.

Answer 2

To “assure” a person of something is to make him or her confident of it. According to Associated Press style, to “ensure” that something happens is to make certain that it does, and to “insure” is to issue an insurance policy. Other authorities, however, consider “ensure” and “insure” interchangeable. To please conservatives, make the distinction. However, it is worth noting that in older usage these spellings were not clearly distinguished.European “life assurance” companies take the position that all policy-holders are mortal and someone will definitely collect, thus assuring heirs of some income. American companies tend to go with “insurance” for coverage of life as well as of fire, theft, etc.

"assure" Definitions:

1. (v) make certain of
2. (v) inform positively and with certainty and confidence
3. (v) assure somebody of the truth of something with the intention of giving the listener confidence
4. (v) be careful or certain to do something; make certain of something
5. (v) cause to feel sure; give reassurance to
6. (v) make a promise or commitment

"assure" Usages:

1. Soon the Great Depression in the 1930s showed that democracy could not assure prosperity either, and the totalitarian creeds gathered momentum.
2. In all of these markets, reform must assure transparency, prevent abuse, and protect the public interest.
3. Conversely, oil companies might sell futures contracts to assure a profit against future price drops.

"ensure" Definitions:

1. (v) make certain of
2. (v) be careful or certain to do something; make certain of something

"ensure" Usages:

1. Senator Bordallo has been fighting to ensure that the people of Guam have a voice in Washington.
2. To ensure that as many Democrats as possible can cast their votes.
3. While we do not know all the details of this arrangement, the Fed must ensure that the plan protects the families that count on insurance.

"insure" Definitions:

1. (v) be careful or certain to do something; make certain of something
2. (v) make certain of
3. (v) protect by insurance
4. (v) take out insurance for

"insure" Usages:

1. AIG generally sells credit-default swaps, thereby promising to insure others against defaults.
2. Some facts about 1944 movie tastes, as registered at the nation's box-offices: A popular star does not insure a popular picture.
3. Say you buy a house and insure it.

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