[sure] adj sur.er ; sur.est [ME, fr. MF sur, fr. L securus secure] (13c) 1 obs: safe from danger or harm
2: firmly established: steadfast "a ~ hold"
3: reliable, trustworthy
4: marked by or given to feelings of confident certainty "I'm ~ I'm right"
5: admitting of no doubt: indisputable "spoke from ~ knowledge"
6. a: bound to happen: inevitable "~ disaster" b: bound, destined "is ~ to win" 7: careful to remember, attend to, or find out something "be ~ to lock the door" -- sure.ness n -- for sure : without doubt or question: certainly -- to be sure : it must be acknowledged: admittedly syn sure, certain, positive, cocksure mean having no doubt or uncertainty. sure usu. stresses the subjective or intuitive feeling of assurance "felt sure that I had forgotten something". certain may apply to a basing of a conclusion or conviction on definite grounds or indubitable evidence "police are certain about the cause of the fire". positive intensifies sureness or certainty and may imply opinionated conviction or forceful expression of it "I'm positive that's the person I saw". cocksure implies presumptuous or careless positiveness "you're always so cocksure about everything".
[2]sure adv (14c): surely usage Most commentators consider the adverb sure to be something less than completely standard; surely is usu. recommended as a substitute. Our current evidence shows, however, that sure and surely have become differentiated in use. Sure is used in much more informal contexts than surely. It is used as a simple intensive "I can never know how much I bored her, but, be certain, she sure amused me --Norman Mailer" and, because it connotes strong affirmation, it is used when the speaker or writer expects to be agreed with "it's a moot point whether politicians are less venal than in Twain's day. But they're sure as the devil more intrusive --Alan Abelson" "he sure gets them to play --D. S. Looney". Surely, like sure, is used as a simple intensive "I surely don't want to leave the impression that I had an unhappy childhood --E. C. Welsh" but it occurs in more formal contexts than sure. Unlike sure it may be used neutrally--the reader or hearer may or may not agree "it would surely be possible, within a few years, to program a computer to construct a grammar --Noam Chomsky" and it is often used when the writer is trying to persuade "surely a book on the avant-garde cannot be so conventional --Karl Shapiro".