certainly and surely

SURELY AND CERTAINLY

1. SURELY, NOT THE SAME AS CERTAINLY.

Surely does not usually mean the same as certainly. Compare:

That’s certainly a plain-clothes policeman. (= I know that is a plain-clothes policeman).

Surely that’s a plain-clothes policeman? (= That really seems to be a plain-clothes policeman. How surprising!)

2. SURELY MEANING: BELIEF IN SPITE OF…

Surely is normally used to say that the speaker believes something in spite of appearances, in spite of reasons to believe the opposite, or in spite of suggestions to the contrary. Sentences with surely often have question marks.

Surely that’s Henry over there? I thought he was in Scotland.

“I’m going to marry Sonia.” “Surely she’s married already?”

“Is it tonight we’re going out?” “No, tomorrow, surely.”

Surely (with heavy stress) can suggest that the speaker would like to believe something, but is beginning to lose hope.

Surely she’s going to stop crying soon? (it looks as if she’s going to go on forever).

Surely not expresses difficulty in believing something.

Surely you’re not going out in that hat?

“Tim failed his exam.” “Oh, surely not?”

You don’t think I’m going to pay for you, surely?

© Michael Swan, Practical English Usage, Oxford