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motive power; driving force
好奇心が研究の原動力だ。
Curiosity is the driving force behind research.
家族の応援が彼の原動力になっている。
His family's support is his driving force.
経済成長の原動力となる産業を育てることが重要だ。
It's important to nurture industries that serve as the driving force for economic growth.