tr.v. as·sured, as·sur·ing, as·sures
1. To inform positively, as to remove doubt: assured us that the train would be on time.
2. To cause to feel sure: a gesture that assured her of his devotion.
3. To give confidence to; reassure.
4. To make certain; ensure: "Nothing in history assures the success of our civilization" (Herbert J. Muller).
5. To make safe or secure: "We would rather forgo certain benefits in order to be assured against certain evils" (Alfred E. Smith).
6. Chiefly British To insure, as against loss.
[Middle English assuren, from Old French assurer, from Vulgar Latin *assēcūrāre, to make sure : Latin ad-, ad- + Latin sēcūrus, secure; see SECURE.]
as·surer, as·suror n.
Usage Note: Assure, ensure, and insure all mean "to make secure or certain." Only assure is used with reference to a person in the sense of "to set the mind at rest": The ambassador assured the prime minister of his loyalty. Although ensure and insure are generally interchangeable, only insure is now widely used in American English in the commercial sense of "to guarantee persons or property against risk."
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2018 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.