vigor

尽管年过六十，他依然保持着年轻人的活力。

Despite being over sixty, he still maintains the ___vigor of a young man.

她以极大的干劲创办了初创公司，投资者立刻注意到了她。

She launched her startup with such ___vigor that investors immediately took notice.

辩论队队长以如此猛烈的劲头辩论，对手们都沉默了。

The debate team captain argued with such ___vigor that his opponents fell silent.