Synonyms for surely

absolutely, affirmatively, assuredly, categorically, certainly, conclusively, definitely, dependably, doubtless, doubtlessly, incontestably, incontrovertibly, indeed, indisputably, indubitably, inescapably, inevitably, positively, precisely, truly, uh-huh, unarguably, unavoidably, undeniably, undoubtably, undoubtedly, unerringly, unmistakably, unquestionably, without doubt, without question, yea, yep, yup