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

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

  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


  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.>

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).


February 13, 2016

a trying or distressing experience

Get Word of the Day daily email!


Take a 3-minute break and test your skills!


How much does a batman (the Turkish unit of measurement) weigh?

2.2 pounds 196.5 pounds 16.96 pounds 100 pounds
Name That Thing

10 quick questions: hear them, spell them, and see how your skills compare to the crowd.


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