Pressure
The perpendicular force exerted per unit surface area over which that force is distributed.
Governing formula
P = F / A
SI unit
Pa
In depth
Pressure in fluids acts equally in all directions (Pascal's law) and arises from microscopic molecular collisions against container walls. Standard atmospheric pressure at sea level is 101,325 Pa (1 atm).
Examples in the real world
High pressure exerted by the sharp point of a thumbtack compared to a flat hammer, or blood pressure measured in millimeters of mercury (mmHg).