Quick answer: Assure means to tell someone confidently that something is true or will happen, removing their doubt: I assure you the flight is on time. Insure means to arrange a contract that provides financial compensation for loss, damage, illness, or death: You should insure your car. A third word, ensure, means to make certain something happens — don't mix up all three. For a fuller definition, see the Cambridge Dictionary entry for ‘assure’.
Comparison Table
| Word | Part of Speech | Meaning | Example |
|---|---|---|---|
| assure | verb | to tell someone confidently that something is true or will happen, removing doubt | I assure you everything is under control. |
| insure | verb | to arrange a contract providing financial compensation for loss, damage, or death | She insured her house against fire and flood. |
Using Assure
Assure is a verb meaning to make someone feel certain about something, usually by stating it confidently. It always takes a person as its direct object (you assure someone).
I assure you that your data is completely safe.
The doctor assured the patient that the surgery was routine.
He assured his parents he would call every week.
Rest assured, the package will arrive on time.
Using Insure
Insure is a verb meaning to buy or provide an insurance policy that protects against financial loss. In British English, assure (and assurance) is sometimes used specifically for life insurance, while insure covers most other risks.
We insured the shipment for its full value.
You must insure your vehicle before driving it on public roads.
The gallery insured the painting for two million pounds.
Many landlords require tenants to insure their belongings.
Memory Trick
Think of the -SURE in both words differently: asSURE is about making someone feel sure (confident) with words. InSURE shares its root with insurance — if you can replace the word with "take out insurance for", use insure.
Common Mistakes
✗ I insure you that the report is accurate.
✓ I assure you that the report is accurate.
✗ Did you assure the car before the trip?
✓ Did you insure the car before the trip?
✗ Please assure that the door is locked.
✓ Please ensure that the door is locked.
Ensure means "to make certain"; it does not take a person as its object the way assure does.
Tips to Avoid Confusion
- If you are giving someone confidence with words, use assure.
- If you are talking about an insurance policy or financial protection, use insure.
- If you mean "make certain" (with a fact, not a person), the word you probably want is ensure, not assure.
- In British English, life assurance is a common alternative to life insurance — but car, home, and travel cover always use insurance.
For more on related grammar, see reporting verbs. Also confusing: Assume vs Presume, Advise vs Advice, Allow vs Let. Browse all confusing word pairs →
Quick Check: Assure or Insure?
4 fill-in-the-blank questions — choose the correct word for each sentence.
1. “I ___ you the results will be ready by Friday.”
2. “You should ___ your home against flood damage.”
3. “The manager ___ the staff that no jobs would be cut.”
4. “He ___ his motorbike for a year before selling it.”
Frequently Asked Questions
What is the difference between assure and insure?
Assure means to tell someone confidently that something is true or will happen, removing their doubt: "I assure you the report is accurate." Insure means to arrange a contract of insurance that provides financial compensation for loss, damage, or death: "You must insure your car." The two verbs are related in spelling but used in completely different situations.
Is assure the same as ensure?
No. Assure means to give someone confidence about something, and it takes a person as its object: "I assure you." Ensure means to make certain that something happens, and it usually takes a fact or situation as its object, not a person: "Please ensure the door is locked." You cannot "ensure someone" in the way you can "assure someone".
Can you insure a person's life?
Yes. Life insurance (also called life assurance in British English) is a contract that pays out money when the insured person dies. You would say "He insured his life for £200,000" or, more formally in the UK, "He took out a life assurance policy."
What does 'rest assured' mean?
'Rest assured' is a fixed phrase meaning "you can feel confident/certain": "Rest assured, your booking has been confirmed." It always uses assure (in its adjective form assured), never insure, because it is about giving confidence, not financial protection.
Why do British insurance companies use the word 'assurance' sometimes?
In traditional British usage, assurance was used for insurance policies that were certain to pay out eventually, such as life assurance (since everyone eventually dies), while insurance was used for policies covering uncertain events, like fire or theft. Today the distinction has blurred, but "life assurance" is still common in the UK.
What part of speech are assure and insure?
Both are verbs. Assure is often followed by a person plus a that-clause: "I assure you that it's true." Insure is often followed by a direct object (the thing being insured) plus 'against' or 'for': "insure the car against theft" or "insure it for £5,000."
Can 'assure' be used without a person as the object?
Rarely in modern usage — assure almost always takes a person: "assure someone (that)...". If there is no person, you likely need a different verb, such as ensure or confirm, depending on meaning.
What is the adjective form of assure?
The adjective is assured, meaning confident or guaranteed: "She spoke in an assured tone." "Success is not assured." There is no equivalent common adjective form of insure used this way.
What is a real-world example combining all three words — assure, ensure, insure?
"I assure you (give you confidence) that we will ensure (make certain) your goods are insured (financially protected) during shipping." This sentence uses all three correctly in one context.
How can I remember assure vs insure for exams?
Link assure to reassure and confidence — both relate to feelings of certainty given through words. Link insure to insurance and money — both relate to financial contracts. If money or a policy is involved, choose insure; if confidence or a promise is involved, choose assure.