Proof
Etymology
From Latin "probare" (to test, examine, judge as good), from "probus" (good, upright) — the same root behind probe, probable, probity, and approve. To prove was first to test, not to confirm; the old saying "the exception proves the rule" preserves this — it tests the rule, doesn’t confirm it. Alcohol "proof" comes from the same idea of testing strength.
noun · /PROOF/
Evidence or reasoning sufficient to establish that something is true.
What it names
A handle for the standard that ends doubt — and for how rarely, outside mathematics, we actually reach it.
Example
She had plenty of evidence he was lying, but nothing she would call proof.
Related idea
Distinguish proof from evidence: evidence nudges a belief up or down; proof is meant to settle it. Genuine proof lives mainly in mathematics and logic — in courts and science we work with standards like "beyond reasonable doubt" or strong evidence, and calling those "proof" overstates what we have.
noun · /PROOF/
A measure of the alcohol content of a spirit.
What it names
the strength of distilled liquor
Example
The whiskey was bottled at 100 proof, or 50 percent alcohol.
Related idea
The term for a spirit’s strength, set at roughly twice the alcohol percentage; it rides along with distill, the process that concentrates that alcohol, and has nothing to do with proving something true.
noun · /PROOF/
A trial print made to be checked and corrected before final printing.
What it names
a preliminary copy for correction
Example
The author marked errors on the galley proofs.
Related idea
A proof is the test copy pulled so mistakes can be caught before the run — closer to a rough draft you correct than to the ‘evidence’ sense, though both trace back to putting something to the test.
See also