/ˈɪmpɪtəs ||; ˈɪmpətəs/noun [U] [sing]
(an) impetus (for sth);
(an) impetus (to do sth) something that encourages sth else to happen 推动力:
This scandal provided the main impetus for changes in the rules. 这宗丑闻成为修改规章制度的主要推动力。I need fresh impetus to start working on this essay again. 我需要新的推动力，才能重新动笔写这篇短文。