---
title: ensure vs insure vs assure
canonical_url: https://ensurance.app/guide/ensure-vs-insure-vs-assure
markdown_url: https://ensurance.app/guide/ensure-vs-insure-vs-assure.md
subtitle: "the usage answer in one table, then the history: how one anglo-norman word became three english ones — and which one lost its noun"
category: philosophy
---

# ensure vs insure vs assure

*the usage answer in one table, then the history: how one anglo-norman word became three english ones — and which one lost its noun*

**Ensure** means to make certain that something happens. **Insure** means to arrange cover against a loss in exchange for a premium; American English also accepts it for "make certain." **Assure** means to tell someone something confidently so they stop worrying — and, in British usage, to cover a life. Three spellings, one root, one meaning that split by convention.

| word | what it means today | example | note |
|---|---|---|---|
| ensure | make certain that something happens | *The culvert was sized to ensure the road stays open.* | the general-purpose verb everywhere |
| insure | arrange cover against a loss, for a premium | *The county insured the bridge for replacement cost.* | US English also uses it for *ensure*; British English keeps them apart |
| assure | tell someone confidently; remove their doubt | *The engineer assured the board the slope would hold.* | in Britain, also life cover: *life assurance* |

That is the usage answer. The rest of this post is the history — how one Anglo-Norman word became three English ones, which spelling the seventeenth-century trade often used, and why the noun with the *e* is the one that got lost.

The thing all three words are about — being sure of something — is older than any of them, and so is the thing we use them for. The hillside held before anyone promised to pay if it did not. The words describe people's relationship to that fact: a promise made, a payment arranged, a worry set down. [Ensurance](/manual/ensurance?from=guide), in our use, is the payment that keeps the hillside working. It is a word about money and care. The hillside is neither.

## one word, three spellings

All three come from Latin *securus*, "free from care." Two of them — *ensure* and *insure* — are the same word. French spelling variants carried both *en-* and *in-* forms into English, and most *en-* words had an *in-* twin at some point. The third, *assure*, is a separate French line (*asseurer*, from *ad-* + *securus*), but English used it interchangeably with the other two. Where the root came from, and what the medieval verb could do, is in [free from care](/guide/free-from-care-where-the-word-insurance-comes-from?from=guide).

| spelling | first English use | what it carried |
|---|---|---|
| assurance | late 1300s | a general pledge; then **the first commercial word** for marine cover, late 1500s |
| ensurance | 1469 | a pledge, a betrothal, making certain; **used in the trade in the 1600s, alongside *insurance*** |
| insurance | before 1556 | a variant of *ensurance*; a betrothal at first; **commercial from the 1650s** |

## the first commercial word was assurance

When London's merchants first needed a word for paying to be covered against the loss of a ship, the word they used was *assurance*.

In the 1570s London set up an **Office of Assurances** in the Royal Exchange, with a registrar and a merchants' court that sat twice a week in his rooms. Thirty-nine London policies survive from 1573 to 1593; the average sum insured was £527. In 1601 Parliament passed "An Acte concerninge matters of Assurances, amongste Merchantes," reforming that court. The 1911 *Encyclopædia Britannica* summed it up: "Assurance was the earlier term, and was used of all forms of insurance indiscriminately till the end of the 16th century."

So the honest sequence is not *ensurance* first. It is *assurance* first, in the trade; *ensurance* alongside it in the 1600s; *insurance* winning in the 1700s.

## then the e entered the trade

Thomas Mun wrote *England's Treasure by Forraign Trade* in the 1620s or 1630s. He died in 1641; the book was printed in 1664, "at the South entrance of the Royal Exchange." A merchant, Mun wrote, "ought to be … expert in the order and form of Charter-parties, Bills of Lading, Invoyces, Contracts, Bills of Exchange, and **policies of Ensurance**," and should "**ensure** his adventures from one Countrey to another" and "be well acquainted with the laws, orders and customes of the **Ensurance office** both here and beyond the Seas."

Others used it too. In 1654 Whitlock's *Zootomia* uses "ensurance of their deniall" in the plain sense of making certain. In 1686 *The Character and Qualifications of an Honest Loyal Merchant* copied Mun's list almost word for word — "Policies of Ensurance," "Ensure his Adventures," and "the Laws, Orders, and Customs of the Ensurance-Offices and Courts of Admiralty." In 1688 a pamphlet on the penal laws, attributed to William Penn, speaks of "Ensurance by Oaths and Tests" — a pledge, not a policy.

For much of that century, then, an English merchant who wanted to be covered could walk into the Ensurance office and take out a policy of ensurance — while the *i* spelling, commercial from the 1650s, was already in use beside it.

## the institutions chose the i

What changed was not the merchants. It was the companies.

After the Great Fire of 1666, Nicholas Barbon opened an **Insurance Office for Houses** behind the Royal Exchange (1680–81), and in 1684 published *A Letter to a Gentleman in the Country, Giving an Account of the Two Insurance-Offices*. The Sun Fire Office followed in 1706, and the companies after it. All of them used *insurance*. Once the word was printed on policies and on the fire marks fixed to insured houses, the spelling followed the business. The 1911 *Britannica* draws a different line — marine against fire, not *e* against *i*: "Insurance — in its earlier form, 'ensurance' — was first applied to fire risks." By the 1700s, either way, the fire offices' spelling was *insurance*.

## 1755: two dictionaries, halfway through the change

The year 1755 catches the word mid-stride. Two English dictionaries appeared that year and disagreed about where the business lived.

| dictionary, 1755 | *ensurance* | *insurance* |
|---|---|---|
| Samuel Johnson, *A Dictionary of the English Language* | "exemption from hazard, obtained by the payment of a certain sum"; *ensurer*: "one who makes contracts of ensurance" | **no separate entry** (still the case in the 1773 edition) |
| Joseph Nicol Scott, *A New Universal Etymological English Dictionary* | "to exempt a thing from hazard by paying a certain sum" | "security given to make good any loss … for a certain premium paid" |

Johnson still filed the trade under the *e*. His is the last major definition under that spelling. The Oxford English Dictionary's last citation for the noun *ensurance* is from 1755, and it marks the word obsolete.

Read Johnson's wording once more: **"exemption from hazard."** In practice an eighteenth-century policy still paid after the loss. But Johnson's phrase names what the buyer was after — to be free of the danger — and that is the sense we use. The phrasing is the dictionary's, not ours.

## how the three settled

| word | settled meaning | how it got there |
|---|---|---|
| **ensure** | make certain that something happens | Dominant from the 1700s. The old sense of pledging *to* someone — "I shall ensure thee" — is marked obsolete |
| **insure** | cover against loss for a premium; in US English also "make certain" | The spellings were still loose in the late 1700s: the US Constitution (1787) sets out to "insure domestic Tranquility." American usage kept that looseness; British usage did not |
| **assure** | tell someone confidently; in Britain, cover a life | In 1826 Charles Babbage proposed *assurance* for events that must happen (death) and *insurance* for events that may. It never fully took, but UK *life assurance* survives |
| **ensurance** (noun) | obsolete since about 1755 | Dictionary.com autocorrects it to *endurance*; Cambridge has no entry |

The division is a convention, not a logic. Nothing in the root says *in-* should take the money and *en-* the outcome. It happened because the companies printed one spelling, and usage, later, sorted the rest.

:::johnson
**the trade took the i. the meaning stayed with the e.** — when *insurance* became the name for the payment after the loss, *ensure* kept "make certain." The noun for that is the one we use.

[the full comparison, side by side →](/guide/ensurance-vs-insurance?from=guide)
:::

## the noun that got lost

Here is the odd outcome of three centuries of sorting. The verb *ensure* won the most general meaning in the language — make certain. Its noun, *ensurance*, died with the trade that stopped spelling it that way.

So a modern reader who stops to parse *ensurance* hears what the grammar tells them: the act of ensuring. Many read it first as a misspelling of *insurance*; the next post is about that. The noun lost its industry and kept its meaning. That is why the word fits what we do with it — funding the present condition of a forest, a wetland, or a reef so that its work keeps going, rather than paying after that work fails — without being bent out of shape.

Three things we do not claim, because the record does not support them:

1. **Not "the original word for insurance."** The first commercial word was *assurance*. *Ensurance* carried the trade mainly in the seventeenth century, alongside *insurance*.
2. **Not "it always meant prevention."** Its old senses are a pledge, a guarantee, a betrothal, and then Johnson's paid-for exemption from hazard. *Make certain* is honest. *Prevention* is our modern sense, and we say so.
3. **Not "we coined it."** We revived it. That is both more accurate and the stronger claim.

What the word means in current use, and what the dictionaries say about it, is in [the word is older than the industry](/guide/the-word-is-older-than-the-industry?from=guide). What it pays for, and how that differs from a policy, is in [ensurance vs insurance](/guide/ensurance-vs-insurance?from=guide).

## frequently asked questions

### what is the difference between ensure and insure?

*Ensure* means to make certain that something happens. *Insure* means to arrange cover against a loss for a premium. They are historically the same word — the noun *insurance* began as a spelling variant of *ensurance* — and English separated them by convention from the 1700s on. American English still accepts *insure* for *ensure*; British English keeps them apart.

### can you use insure to mean ensure?

In American English it is accepted — the Constitution's "insure domestic Tranquility" dates from when the spellings were still loose. British English keeps the two apart. If you want to be understood on both sides of the Atlantic, use *ensure* for "make certain" and *insure* for cover.

### what is the difference between assurance and insurance?

Today, *assurance* means telling someone something confidently, and in Britain it also names life cover. *Insurance* is cover against a loss that may or may not happen. Historically, *assurance* was the first commercial word — London's Office of Assurances dates from the 1570s — and was used for all kinds of cover until the end of the sixteenth century.

### why is it called life assurance in the uk?

*Assurance* was the older trade word. In 1826 Charles Babbage also proposed a distinction: *assurance* for an event that is certain to happen (death), *insurance* for an event that may happen. The distinction was never universal, but British life companies kept the word.

### was ensurance the original word for insurance?

No. *Assurance* was the first commercial word, in the 1570s. *Ensurance* was used in the trade through much of the 1600s, alongside *insurance* — merchants wrote "policies of Ensurance" and spoke of "the Ensurance office" — and Samuel Johnson still filed the business under *ensurance* in 1755, with no separate entry for *insurance*. The *i* spelling won after the fire offices adopted it.

## read next

[can anyone own the word ensurance?](/guide/can-anyone-own-the-word-ensurance?from=guide) — what a trademark actually protects, why a common noun is hard to own, and forty years of brands that borrowed the spelling.

## sources

[Encyclopædia Britannica (1911) — Insurance](https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Insurance) — "Assurance was the earlier term…"; "Insurance — in its earlier form, 'ensurance' — was first applied to fire risks"

[Rossi, "The Booke of Orders of Assurances: A Civil Law Code in 16th Century London," Maastricht Journal 19 (2012)](https://ilc-law.media.uconn.edu/wp-content/uploads/sites/3281/2023/03/Rossi-The-Booke-of-Orders-of-Assurances-A-Civil-Law-Code-in-16th-Century-London.pdf) — the Office of Assurances; 39 surviving policies, average £527; the 1601 Act

[Thomas Mun, England's Treasure by Forraign Trade (printed 1664)](https://socserv.socsci.mcmaster.ca/~econ/ugcm/3ll3/mun/treasure.txt) — "policies of Ensurance"; "ensure his adventures"; "the Ensurance office"

[The Character and Qualifications of an Honest Loyal Merchant (London, 1686)](https://ota.bodleian.ox.ac.uk/repository/xmlui/bitstream/handle/20.500.12024/A78578/A78578.html?sequence=5&isAllowed=y) — "Policies of Ensurance"; "Ensurance-Offices"

[Nicholas Barbon, A Letter to a Gentleman in the Country, Giving an Account of the Two Insurance-Offices (1684)](https://quod.lib.umich.edu/e/eebo/A30884.0001.001/1:1?rgn=div1;view=fulltext) — the fire offices' spelling

[Insurance Museum — Rising from the ashes](https://insurance.museum/rising-from-the-ashes) — Barbon's Insurance Office for Houses after 1666

["To Insure Domestic Tranquility and Provide for the Common Defence," Hastings Constitutional Law Quarterly](https://repository.uclawsf.edu/cgi/viewcontent.cgi?article=2224&context=hastings_constitutional_law_quaterly) — Johnson 1755 and Scott 1755 definitions

[Johnson's Dictionary Online — ensurance](https://johnsonsdictionaryonline.com/views/search.php?term=ensurance) — the 1755 and 1773 headword *Ensu'rance*: "exemption from hazard, obtained by the payment of a certain sum"; a search for *insurance* returns no entry

[Oxford English Dictionary — ensurance, n.](https://www.oed.com/dictionary/ensurance_n) — obsolete; last citation 1755

[Online Etymology Dictionary — en-](https://www.etymonline.com/word/en-) — *en-* / *in-* variants; [insurance](https://www.etymonline.com/word/insurance) — commercial sense from the 1650s

[Babbage, A Comparative View of the Various Institutions for the Assurance of Lives (1826) — Warwick WRAP summary](https://wrap.warwick.ac.uk/id/eprint/20558/) — the assurance / insurance distinction

## the series

Read first: [the word is older than the industry](/guide/the-word-is-older-than-the-industry?from=guide) — what the word means today and what the dictionaries say.

- [free from care: where the word insurance comes from](/guide/free-from-care-where-the-word-insurance-comes-from?from=guide)
- [ensure vs insure vs assure](/guide/ensure-vs-insure-vs-assure?from=guide)
- [can anyone own the word ensurance?](/guide/can-anyone-own-the-word-ensurance?from=guide)