quickly, effectively, and confidently

If we had acted earlier and more decisively it might not have come to this. 如果我们更早更果断采取行动，事情可能不会走到这一步。

He decisively changes lane with no signal. 他果断地在没打信号的情况下转换车道。

in a way that strongly affects how a situation will progress or end

The electorate voted decisively to change the country's electoral system. 选民果断投票以改变该国的选举制度。

My bet is that she will decisively win the next election. 我敢打赌，她将决定性地赢得下届选举。