Assure vs. Ensure vs. Insure: Basic Rules Of Grammar

We all have those certain words or basic rules of grammar that stump us every time. Whether it’s a tricky spelling or a slightly confusing set of similar-sounding words (like assure vs. ensure vs. insure), there’s no shame in double-checking to ensure you’re getting your word choice right. (See what we did there?)

Assure, ensure and insure can often be confused for one another. If you’re wondering which one to use, or whether they can be used interchangeably, you’re not alone.

Let’s dive into the meanings behind each word and the particulars of their usage.

What does assure mean?

In terms of its most common definition, assure means to state something positively or confidently in order to remove doubt.

Other variations on its usage are essentially similar, including to pledge, promise or make sure of something.

Generally, when using assure as a verb, you will use it in terms of a person. So it can be handy to remember that assure is something you do to another person or to yourself.

Usage examples

Let’s take a look at some examples of assure used in a sentence.

The event will go ahead tomorrow, I assure you.

She checked the dictionary to assure herself that her word choice was correct.

With the promise of reinforcements, their victory was assured.

And from the New York Times:

Obama Assures Disabled Veterans They Will Get Aid

What does ensure mean?

The basic definition of ensure is to make certain that something will happen.

Basically, it refers to the action of securing a particular outcome for a situation.

Contrary to assureensure does not involve doing something to a person, but rather doing something in general to guarantee something will occur or come about.

Usage examples

Let’s take a look at some examples of ensure used in a sentence.

I will ensure that there are enough tables for the event tomorrow.

A successful interview ensured her a job with the company.

The captain called all his soldiers to arms to ensure they would win the battle.

And from the New York Times:

Obama Signs Bill to Ensure Military Will Be Paid During Shutdown

assure vs ensure vs insure

What does insure mean?

The definition of insure is a little different – it has a less flexible meaning (more on that below). To insure something means to arrange for compensation in case of loss or damage to an item, or the injury, illness or death of a person.

This usually refers to the purchase of a policy, wherein payments are made to an insurance company, which will pay compensation if something happens to whatever has been insured.

Insure was once more commonly used interchangeably with ensure. While some publications and style guides still use it this way, most do not. If you want to be on the safe side, stick with using insure in terms of its use regarding policies or measures taken against risk.

Usage examples

Let’s take a look at some examples of insure used in a sentence.

The venue is offering the option to insure your tickets for tomorrow’s event in case it is cancelled.

I recently purchased a new policy to insure my car.

When you own valuable property, it’s important to insure against loss.

And from the New York Times:

The Least (and Most) Expensive Cars to Insure

Are assure, ensure and insure interchangeable?

To summarise the above: while assureensure and insure are similar-sounding words that all have something to do with ‘making sure’ or ‘guaranteeing’ in some sense, they are not directly interchangeable. Each word means something slightly different.

Ensure and insure can still be used interchangeably in some cases, but these days, they are more commonly used for their own separate meanings and purposes.

Word Origins

For all the word nerds out there, we thought we’d delve quickly into the origins of each of these words…

Assure origin

Originating in Late Middle English (around the 14th century), from the Old French assurer, meaning ‘to reassure, calm, protect, to render sure’, assure has its roots in the Latin ad+securus (ad meaning ‘to’, securus meaning ‘secure’ or ‘safe’).

Ensure origin

Also originating in Late Middle English (late 14th century), ensure took the form of ensuren, stemming from from the Anglo-French ensuerer – en meaning ‘make’, suer meaning ‘sure’.

Insure origin

Originating a little further on in Late Middle English (around the mid-15th century), insure began as insuren, a spelling variant of ensuren. Around the mid-17th century, it took on its particular financial/compensation-related meaning, which has become its primary meaning today.

assure vs ensure vs insure


If you’re looking for alternatives to these words, perhaps try some of the following…

Assure synonyms

  • Affirm
  • Reassure
  • Convince
  • Persuade
  • Promise

Ensure synonyms

  • Establish
  • Secure
  • Make sure
  • Make certain
  • Guarantee

Insure synonyms

  • Cover
  • Protect
  • Safeguard
  • Indemnify
  • Underwrite


So that’s it, writers! We hope this has cleared up any confusion regarding assure vs. ensure vs. insure.

For more writing tips and advice, be sure to check out our hundreds of articles about fiction writing.

Claire Bradshaw

Claire is a freelance editor and proofreader based in Newcastle, Australia. She works with indie and traditional authors to prepare their works for publication, primarily editing fantasy novels. In her spare time, you might find her reading, birdwatching or drinking endless cups of tea while writing things of her own. Click here to visit Claire's website.

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