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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·sur′er, as·sur′or 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."