Gravity

Etymology

From Latin "gravitas" (weight, heaviness, also seriousness), from "gravis" (heavy). Newton borrowed the everyday word for heaviness and turned it into the universal attraction between masses; Einstein later recast it as the curving of spacetime.

noun · /GRAV-ih-tee/
The attraction every mass exerts on every other mass — what pulls objects toward Earth and holds planets in orbit.
What it names
One force, the common cause of falling apples, ocean tides, and planetary orbits, which look unrelated until you see the single rule underneath.
Example
Gravity is weaker on the Moon, so the same astronaut who weighs 180 pounds on Earth weighs about 30 there.
Related idea
Gravity is the force; mass is what generates and responds to it. Your mass is fixed everywhere, but the gravitational force on it — your weight — changes with where you stand.
noun · /GRAV-ih-tee/
The quality of being serious, weighty, or solemn — the seriousness of a situation or of someone's manner.
What it names
It lets one word carry both a physical pull and a moral one, so 'the gravity of the crisis' means its heaviness of consequence.
Example
The judge's tone made the gravity of the charges unmistakable.
Related idea
The opposite of the arch or the flippant — gravity is genuine weight of feeling or consequence, so 'the gravity of the crisis' means the heaviness the situation itself carries.