Learner's definition of CERTAINTY
the state of being or feeling certain about something
Scientists still do not know with any degree of certainty why the disease spread so quickly.
We cannot predict the outcome with absolute/any certainty.
There was no certainty that the package would arrive in time.
Her certainty about these complex moral issues is surprising.
It is difficult to say with certainty [=in a certain or definite way] which of the plays was written first.
something that is certain
a fact about which there is no doubt