sure

Most commentators consider the adverb sure to be something less than completely standard; surely is usually 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