assure

verb

as·​sure ə-ˈshu̇r 

assured; assuring

transitive verb

1

: to make sure or certain : convince

glancing back to assure himself no one was following

2

: to inform positively

I assure you that we can do it.

3

: to make certain the coming or attainment of : guarantee

worked hard to assure accuracy

4

: to make safe (as from risks or against overthrow) : insure

assured the security of the country

5

: to give confidence to

And hereby we know that we are of the truth, and shall assure our hearts …

—1 John 3:19 (King James Version)

Usage of Assure, Ensure, and Insure

In the centuries that ensure, assure, and insure have been in use, each member of the trio has at times been defined as a synonym of the others. Today, however, distinctions are generally made. Assure is most often used when someone is removing, or attempting to remove, doubt.

assuring us that the information was correct

Ensure typically applies when something is made sure, certain, or safe.

ensure that the door is locked

Insure sometimes has this same meaning, but more often it is used when insurance is involved,

insure the car against theft

or, with the word against, when there is an effort to prevent something.

trying to insure against a negative outcome

Synonyms of assure

• reassure
• comfort
• soothe

Choose the Right Synonym for assure

ensure, insure, assure, secure mean to make a thing or person sure.

ensure, insure, and assure are interchangeable in many contexts where they indicate the making certain or inevitable of an outcome, but ensure may imply a virtual guarantee,

the government has ensured the safety of the refugees

while insure sometimes stresses the taking of necessary measures beforehand,

careful planning should insure the success of the party

and assure distinctively implies the removal of doubt and suspense from a person's mind.

I assure you that no harm will be done

secure implies action taken to guard against attack or loss.

sent reinforcements to secure their position

Examples of assure in a Sentence

I can assure you that you won't be disappointed.

a minister choosing just the right words to assure the grieving parents of the fallen soldier

Recent Examples on the Web

Pelle Larsson added 20 points and a career-high 10 rebounds for Miami (40-36), which kept some realistic hope of getting out of the play-in tournament range — or at least getting into one of the top two spots and therefore assuring itself two chances of making the playoffs — alive with the win. —CBS News, 31 Mar. 2026

Rest assured that here too, under the gold-leaf ceiling, you may be seated next to luminaries of Rome’s cultural and political scenes. —Condé Nast, Condé Nast Traveler, 31 Mar. 2026

Migdalia Perez, a partner at Perez LaSure Law, assured the judge there was no conflict. —Cristóbal Reyes, The Orlando Sentinel, 31 Mar. 2026

Under the current system, parents and hospitals can be assured that medical treatments will be covered. —Selena Simmons-Duffin, NPR, 31 Mar. 2026

Word History

Etymology

Middle English, from Anglo-French asseurer, assurer, from Medieval Latin assecurare, from Latin ad- + securus secure

First Known Use

14th century, in the meaning defined at sense 4

Phrases Containing assure

• assure oneself

Rhymes for assure

• abjure
• adjure
• allure
• brochure
• cocksure
• coiffure
• contour
• couture
• demure
• detour
• endure
• ensure

Kids Definition

assure

verb

as·​sure ə-ˈshu̇(ə)r 

assured; assuring

1

: to provide a guarantee of

assure security

2

: to give words of comfort or confidence to : reassure

tried to assure the worried children

3

: to cause to be sure or certain

assure himself that the door was locked

4

: to inform positively

can assure you of her dependability

Legal Definition

assure

transitive verb

as·​sure

assured; assuring

1

chiefly British : insure

2

a

: to inform positively

the seller assured the buyer of his honesty

b

: to provide a guarantee of