Definition of "Assure" :
verb: be careful or certain to do something; make certain of something
verb: assure somebody of the truth of something with the intention of giving the listener confidence
"I assured him that traveling to Cambodia was safe."
verb: make a promise or commitment
verb: make certain of
verb: inform positively and with certainty and confidence
verb: cause to feel sure; give reassurance to
"The airline tried to reassure the customers that the planes were safe."