im·pe·tus /ˈɪmpətəs/ noun
a force that causes something (such as a process or activity) to be done or to become more active [noncount
] ▪ His discoveries have given impetus to further research. ▪ The movement is now gaining/losing impetus. [=momentum]
] ▪ Her work provided the major impetus [=stimulus] behind the movement.
— often + for ▪ The tragic accident became an impetus for changing the safety regulations.
— sometimes followed by to + verb ▪ His discoveries have given researchers the impetus to try something new.
] technical :
a force that causes an object to begin moving or to continue to move