Synonyms for With certainty:

• adv.

  •positively (adverb)
  • flat out,
  • no kicker,
  • flat,
  • assuredly,
  • easily,
  • on the money,
  • the ticket,
  • for a fact,
  • no catch,
  • undeniably,
  • firmly,
  • right on,
  • unmistakably,
  • Doubtlessly,
  • categorically,
  • no holds barred,
  • amen,
  • really truly,
  • to a tee,
  • no ifs ands or buts,
  • no strings attached,
  • emphatically,
  • unequivocally,
  • doubtless,
  • without qualification,
  • certainly,
  • undoubtedly,
  • sure,
  • unquestionably,
  • indubitably,
  • on the nose.
  •surely (adverb)
  • decidedly,
  • indeed,
  • conclusively,
  • plainly,
  • evidently,
  • clearly,
  • distinctly,
  • inevitably,
  • absolutely,
  • definitely.

• Other synonyms:

  •
  • surely.

Antonyms for With certainty:

• adv.

  • positively
    doubtfully, questionably.
  • surely
    dubiously, indefinitely, uncertain, indefinite, vaguely.