surely

Synonyms: absolutely admittedly assuredly beyond doubt beyond shadow of doubt certainly clearly come what may conclusively decidedly definitely distinctly doubtlessly evidently explicitly fixedly for certain for real indeed indubitably inevitably inexorably infallibly irrefutably manifestly nothing else but plainly positively rain or shine to be sure undoubtedly unequivocally unerringly unfailingly unmistakably unquestionably unshakably with certainty without fail

Antonyms: doubtfully questionably uncertain