impetus
/ˈɪmpɪtəs ˈइम्पिटस्/ noun [U, usually sing.] (an) impetus (for something) ; (an) impetus (to do something) something that encourages something else to happen ऐसी वस्तु जो दूसरी वस्तु की क्रियाशीलता को बढ़ावा दे; प्रेरणा, प्रोत्साहन
This scandal provided the main impetus for changes in the rules.
I need fresh impetus to start working on this essay again.