impetus

1 ENTRIES FOUND:
impetus /ˈɪmpətəs/ noun
impetus
/ˈɪmpətəs/
noun
Britannica Dictionary definition of IMPETUS
1 
: a force that causes something (such as a process or activity) to be done or to become more active
[noncount]
[singular]
— often + for
— sometimes followed by to + verb
2 
[noncount] technical : a force that causes an object to begin moving or to continue to move