I . ad.
1.
Truly, really, veritably, verily, positively, absolutely, certainly, in fact, in truth, in reality.
2.
Strictly, strictly speaking, to tell the truth, in point of fact, in fact, in fine, as a matter of fact.
II . interj.
Really, is it so, you don't say so, who'd have thought it, is it possible, Heaven save the mark.