impetus

noun

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”).

1. Anything that impels; a stimulating factor.

   “The outbreak of World War II in 1939 gave a new impetus to receiver development.”

   “Once set a strong mind thinking, and you have done all that it needs for its education. It matters little what is the first impetus, so that it only be set to work.”

2. A force, either internal or external, that impels; an impulse.
3. The force or energy associated with a moving body; a stimulus.
4. A principle of motive force, held as equivalent 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.