decisive
/di-ˈsī-siv/
adjective
having the power or quality of deciding
resolute, determined
unmistakable, unquestionable
The council president cast the decisive vote.
conclusive decisive determinative definitive mean bringing to an end. conclusive applies to reasoning or logical proof that puts an end to debate or questioning. decisive may apply to something that ends a controversy, a contest, or any uncertainty.
noun
an action or actions done quickly and with confidence
In emergency situations, one must be able to take decisive action.
noun
the most important reason
Cost was the decisive/deciding/determining factor in their decision.