Conclusive describes evidence or arguments that are so strong they settle a question or end debate. It leaves little or no room for doubt.
From Late Latin 'conclūsīvus', from 'conclūdere' ('to close, to finish'). The word keeps the sense of closing a matter so firmly that it cannot easily be reopened.
Conclusive evidence is like the last puzzle piece that makes the whole picture obvious. In real life, we often act on 'good enough' evidence, so truly conclusive proof is rarer than people think.
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