1. for certain - Adverb
2. for certain - Phrase
definitely or positively (`sure' is sometimes used informally for `surely')
Source: WordNetWar is smaller in scale than in recent memory, but it is far more ambiguous, intractable, and nasty. Money flows more quickly than ever, but it is still somehow manages to gather and puddle in certain places, for certain people rather then others. Mark Kingwell
So true is it that all transactions of preeminent importance are wrapt in doubt and obscurity; while some hold for certain facts the most precarious hearsays, others turn facts into falsehood; and both are exaggerated by posterity. Tacitus
We should see the leadership from the White House setting dates certain for certain goals of achieving greater alliance on alternative and renewable energy sources, but we are not. Ron Kind
Everything happens for a reason, and part of that beauty of life is that we're not allowed to know those reasons for certain. Aron Ralston
All I know for certain is that reading is of the most intense importance to me; if I were not able to read, to revisit old favorites and experiment with names new to me, I would be starved - probably too starved to go on writing myself. Penelope Lively
Of your wife and your tried friend believe nothing but what you know for certain. Spanish Proverb