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to reason; to sum up; to conclude
刑事は早々に犯人だと結論付けた。
The detective hastily concluded who the culprit was.
科学者はデータから結論付けて、論文を書いた。
The scientist drew conclusions from the data and wrote a paper.
急いで結論付けると、大切なことを見落とす。
If you rush to conclusions, you miss important things.