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.
(..) - Yes. - Did you mean it? - Every word. You really think blowing up Parliament's going to make this country a better place? There's no certainty, only opportunity. You can be pretty certain that if anyone does show up... ...Creedy'll black-bag every one of them. People should not be afraid (..)2005 V for Vendetta