Causation
Etymology
From Latin "causatio," from "causa" (a reason, motive, cause — also a lawsuit, the source of our legal "case"). To establish causation is to answer not just whether things move together but why, and courts and scientists alike have long treated that as the harder burden.
noun · /kaw-ZAY-shun/
A relationship in which one thing actually brings about or produces another.
What it names
Use it for the stronger, harder-to-prove claim that changing one thing would change the other — the mechanism, not just the pattern.
Example
The trial was designed to establish causation: did the drug lower blood pressure, or did healthier patients simply take it?
Related idea
Its inseparable foil is correlation: a correlation can be spotted by watching; causation usually has to be earned through controlled experiment, because association alone can’t rule out coincidence or a common cause. "Correlation is not causation" is the single most useful sentence in everyday statistics.