decisive

Decisive means making or showing a decision that solves a problem or ends an argument.

When people talk about something being decisive, they usually mean it's what finally settles the issue or makes things clear. For example, you might say "The new evidence was decisive" to mean that it made all the other facts irrelevant and showed what really happened. In sports, a decisive goal can be the one that wins the game. Sometimes, a person's decision is decisive – like a boss making a choice that affects everyone in the company.