decisive

/di-ˈsī-siv/

borrowed from Middle French & Medieval Latin; Middle French decisif, borrowed from Medieval Latin dēcīsīvus, from Latin dēcīsus, past participle of dēcīdere "to cut off, cut out, mark by cutting, settle, choose as a course of action" + -īvus -ive

adjective

  1. having the power or quality of deciding

  2. resolute, determined

  3. 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

  1. an action or actions done quickly and with confidence

In emergency situations, one must be able to take decisive action.

noun

  1. the most important reason

Cost was the decisive/deciding/determining factor in their decision.