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

Reopening the government The bill would extend government funding through January 30, and assure Democrats of a vote on the health care subsidies next month. —David Lightman, Sacbee.com, 10 Nov. 2025

Community members were quick to assure the woman that her feelings are completely valid given the situation. —Toria Sheffield, PEOPLE, 9 Nov. 2025

Taking the podium, Jaramillo humbly thanked Hudak and his fellow officers for their support and Mayor Vince Lago praised Jaramillo, saying the city was blessed to have him and assured him that Coral Gables would always stand behind him. —Milena Malaver, Miami Herald, 8 Nov. 2025

Rest assured, Griffiths has always collected his full salary. —Miles Socha, Footwear News, 7 Nov. 2025

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