impetus

Etymology

Borrowed from Latin impetus (“a rushing upon, an attack, assault, onset”), from impetō (“to rush upon, attack”), from in- (“upon”) + petō (“to seek, fall upon”).

noun

1. Anything that impels; a stimulating factor.
   The outbreak of World War II in 1939 gave a new impetus to receiver development.
   In a single moment Montenegro and their supporters were given fresh impetus and encouragement. Beciraj tested Hart with a low shot before teenager Phil Jones, on his England debut, suffered an anxious moment when Stevan Jovetic went down under his challenge, leaving the youngster clearly relieved to see referee Stark wave away Montenegro's appeals. 2011, Phil McNulty, Euro 2012: Montenegro 2-2 England
2. A force, either internal or external, that impels; an impulse.
3. The force or energy associated with a moving body; a stimulus.
4. (history, medieval physics) A principle of motive force, held as exquivalent to weight times velocity by John Buridan, in an auxiliary theory of Aristotelian dynamics introduced by John Philoponus, describing projectile motion against gravity as linear until it transitions to a vertical drop and the intellectual precursor to the concepts of inertia, momentum and acceleration in classical mechanics.
5. An activity in response to a stimulus.