His victory in the election is 'almost a certainty'. [=it is nearly certain/definite that he will win the election]
It is difficult to say 'with certainty' [=in a certain or definite way] which of the plays was written first.
Scientists still do not know with any degree of 'certainty' why the disease spread so quickly.
(..) Chloe looked the way Meryl Streep's skeleton would look if you made it walk around Well, I'm still here. But I don't know for how long. That's as much certainty as anyone can give me. But I've got some good news. I no longer have any fear of death. But... I am in a pretty lonely place. (..)1999 Fight Club