Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Medical
  • Scrabble
  • Spanish Central
  • Learner's Dictionary


verb as·sure \ə-ˈshu̇r\

Simple Definition of assure

  • : to make (something) certain

  • : to tell someone in a very strong and definite way that something will happen or that something is true

Source: Merriam-Webster's Learner's Dictionary

Full Definition of assure


  1. transitive verb
  2. 1 :  to make safe (as from risks or against overthrow) :  insure

  3. 2 :  to give confidence to <and hereby we know that we are of the truth, and shall assure our hearts — 1 John 3:19(Authorized Version)>

  4. 3 :  to make sure or certain :  convince <glancing back to assure himself no one was following>

  5. 4 :  to inform positively <I assure you that we can do it>

  6. 5 :  to make certain the coming or attainment of :  guarantee <worked hard to assure accuracy>

Examples of assure in a sentence

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

  2. <a minister choosing just the right words to assure the grieving parents of the fallen soldier>

Origin of assure

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

First Known Use: 14th century

Synonym Discussion of 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>.

ASSURE Defined for Kids


verb as·sure \ə-ˈshu̇r\

Definition of assure for Students


  1. 1 :  to give certainty, confidence, or comfort to <He assured the children all was well.> <She assured herself that the doors were locked.>

  2. 2 :  to inform positively <I assure you that you won't be disappointed.>

  3. 3 :  to provide a guarantee of <assure their safety> <Hard work assures success.>

Law Dictionary


transitive verb as·sure

Legal Definition of assure


  1. 1 chiefly Brit :  insure

  2. 2a :  to inform positively <the seller assured the buyer of his honesty> b :  to provide a guarantee of

Seen and Heard

What made you want to look up assure? Please tell us where you read or heard it (including the quote, if possible).


a division or portion of a pool or whole

Get Word of the Day daily email!


Take a 3-minute break and test your skills!


Which of the following best describes an easily irritated person?

tetchy flashy gregarious superficial
Name That Thing

Test your visual vocabulary with our 10-question challenge!


Test Your Knowledge - and learn some interesting things along the way.