1.decisive是动词decide派生的形容词，基本意思是“决定性的”，即指对于最终结果“起关键性作用的”，常用于某些能够终止争论或竞争，结束忧虑，解除疑惑，排除危险的行为、事件、影响或论点。作此解时，decisive不用于比较等级。
2.decisive还可表示人的性格等“坚决的，坚定的，果断的，勇敢的”。指坚定地或最终成功地解决某一有争议问题的能力或意图。

用作定语
▲～+n.
Your argument was the decisive one.你提供的论据是决定性的。
She has played a decisive role in the peace negotiations.她在和谈中起了关键作用。
I'll take a decisive step.我要迈出决定性的一步。
The team had a decisive victory by winning 20 to 2.那个队以20比2赢了，获得决定性的胜利。
Next Monday could be a decisive day for the magazine.下星期一对这个杂志可能是一个决定性的日子。
The decisive point in his getting the job is that he speaks Greek.他所以能得到这个职位是他会讲希腊语，这一点是起决定性作用的。
They have played a decisive role in building Silicon valley.在硅谷建设中他们起了决定性作用。
It was a decisive battle—we won the war because of it.那是一次决定性的战役，由此我们打赢了那场战争。
That was a decisive factor in his decision to emigrate.那是他决心移居国外的决定因素。
The allies won a decisive victory.盟国取得了决定性的胜利。
The Battle of Sarotoga was a decisive victory for the Americans.萨拉托卡之役的取胜是美国人的一次决定性的胜利。
A decisive person acts quickly and often succeeds.果断的人当机立断，常常成功。
The government must take decisive action on gun control.在枪支管制方面政府必须采取果断措施。
What the firm needs is a strong and decisive leader.公司需要的是一位强有力而又果断的领导。
The general was known for his decisive manner.这位将军素以大刀阔斧的作风而著称。
用作表语
▲S+be+～
It's no good hesitating. Be decisive.犹豫没好处，果断一些。
▲S+be+～+prep.-phrase
Public opinion is decisive on the question.舆论对这个问题起决定性的作用。
Our air force was decisive in winning the war.我们的空军在打赢这场战争中起了决定性作用。
These well-known words, used for many centuries, are decisive for the understanding of what a marriage means.这些众所周知的词语使用了许多世纪，对于理解婚姻的意义具有决定性的作用。
The enemy's lack of inspired leadership was decisive to its defeat, long before a single shot was fired.敌人一枪未放、不战自败，其中决定性的原因是缺乏高明的统帅。
She was very decisive in her handling of the problem.她在处理那个问题上非常果断敢行。
▲It is/was+～+of sb+to-v
It's decisive of you to take the action on this issue.在这个行动上你坚决果断。

［派生词］ decisively adv. 果断地
［同义词］   definite, determined, firm
［反义词］   indecisive, insignificant