proof

noun \ ˈprüf \

Updated on: 16 May 2018

1 a : the cogency of evidence that compels acceptance by the mind of a truth or a fact

b : the process or an instance of establishing the validity of a statement especially by derivation from other statements in accordance with principles of reasoning

2 obsolete : experience

3 : something that induces certainty or establishes validity

4 archaic : the quality or state of having been tested or tried; especially : unyielding hardness

5 : evidence operating to determine the finding or judgment of a tribunal

6 a plural proofs or proof : a copy (as of typeset text) made for examination or correction

b : a test impression of an engraving, etching, or lithograph

c : a coin that is struck from a highly polished die on a polished planchet, is not intended for circulation, and sometimes differs in metallic content from coins of identical design struck for circulation

d : a test photographic print made from a negative

7 : a test applied to articles or substances to determine whether they are of standard or satisfactory quality

8 a : the minimum alcoholic strength of proof spirit

b : strength with reference to the standard for proof spirit; specifically : alcoholic strength indicated by a number that is twice the percent by volume of alcohol present

whiskey of 90 proof is 45 percent alcohol

See proof defined for English-language learners

See proof defined for kids

Examples of proof in a Sentence

The document was proof that her story was true.
He claims that he was home when the murder was committed, but he has no proof.
The proof shows that the theorem is true.

Recent Examples of proof from the Web

Within a day of the announcement this week, Dardaman published a proof of concept that showed how the new functionality could be programmed to run the CoinHive cryptomining program through an Excel document.

— lily hay newman, WIRED, "Microsoft's Latest Excel Update Has Security Pros Anxious," 11 May 2018
Those dropping off items must show proof of residency.

— Sun-Sentinel.com, "Fort Lauderdale and Oakland Park area events, May 9-19," 8 May 2018
The fine print: Visitors must present proof of Florida residency at time of purchase and ticket pick-up.

— dewayne bevil, OrlandoSentinel.com, "Universal: Floridians can get 2 days of parks for price of 1," 7 May 2018
The driver was unable to provide a driver's license or proof of insurance.

— bruce geiselman, cleveland.com, "Man faces marijuana charge after bad reaction to gummy candy: North Olmsted police blotter," 5 May 2018
Earlier this year in Greenbelt, Maryland, an amateur paleontologist found a fossil showing distinct proof of mammals and dinosaurs interacting.

— david grossman, Popular Mechanics, "11-Year-Old Stumbles Across 475-Million-Year-Old Fossil," 4 May 2018
Communist propaganda saw proof of America’s duplicity and imperialism.

— The Economist, "George Marshall won the war and rebuilt Europe, but lost China," 3 May 2018
Further proof of that came later, when Avenatti dramatically revealed a new piece of evidence onstage.

— laura bradley, HWD, "Stormy Daniels’s Lawyer Reveals New Evidence that Could Sink Trump’s Case," 3 May 2018
The bill, which requires proof of working 30 hours each week to maintain Medicaid coverage, contains an exemption for people residing in counties where unemployment exceeds 8.5 percent.

— adam k. raymond, Daily Intelligencer, "Michigan’s Proposed Medicaid Work Requirement Comes With a Racist Twist," 3 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'proof.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of proof

Middle English prof, prove, alteration of preve, from Anglo-French preove, from Late Latin proba, from Latin probare to prove — more at prove

NEW! Time Traveler

First Known Use: 13th century

in the meaning defined at sense 1a

See Words from the same year

proof Synonyms

Other Logic Terms

a posteriori, connotation, corollary, inference, mutually exclusive, paradox, postulate, syllogism

proof

adjective

1 : able to resist or repel

boots that were … proof against cold and wet
—Robertson Davies

—often used in combination

windproof

2 : used in proving or testing or as a standard of comparison

3 : of standard strength or quality or alcoholic content

See proof defined for English-language learners

Recent Examples of proof from the Web

Republican lawmakers, however; hold veto-proof supermajorities in both chambers.

— meredith colias-pete, Post-Tribune, "Indiana lawmakers expected to take up Gary school board, school security bills," 11 May 2018
Inspectors have placed some 2,000 tamper-proof seals on nuclear material and equipment, and installed a network of surveillance cameras at nuclear sites.

— Washington Post, "AP FACT CHECK: Trump vs. truth on the Iran nuclear deal," 10 May 2018
Sweet Box shrubs, star jasmine and frost-proof gardenia perfume the air.

— janet eastman, OregonLive.com, "See four private estates during the Dunthorpe Garden Tour (photos)," 9 May 2018
Computers keep tabs on the tamper-proof electronic seals placed by IAEA officials on more than 2,000 pieces of equipment, from storage bins to uranium-processing machines.

— author: joby warrick, Anchorage Daily News, "Muzzled watchdog: How killing the nuclear deal could make it easier for Iran to pursue the bomb in secret," 8 May 2018
For now, Musk expects Neuralink’s proof-of-concept devices to be similar DBS devices to the woman's—that is, devices that use electric impulses to treat conditions such as depression and epilepsy.

— beth mole, Ars Technica, "Don’t charge your brain implant during thunderstorms, docs warn after incident," 5 May 2018
With internet shopping having hurt traditional brick-and-mortar stores so badly in recent years, probably the most internet-proof shopping establishments are supermarkets, where people still go in person to buy perishable food.

— jon lender, courant.com, "Jon Lender: Firm That Got State Loans Hopes Stop & Shop Deal Is Escape Route From Bankruptcy," 5 May 2018
Etude House has a track record of creating life-proof lip products.

— devon abelman, Allure, "K-Pop Group Red Velvet and Etude House Just Launched the $10 Liquid Lipstick of Your Dreams," 4 May 2018
Online learning and micro-certification are increasingly appealing to individuals and businesses seeking to future-proof themselves against automation, or introduce automation without having to fire and rehire a more highly skilled workforce.

— tracey lien, latimes.com, "Algorithms are coming for their jobs, so workers are teaching themselves algorithms," 4 May 2018

First Known Use of proof

1583

in the meaning defined at sense 1

See Words from the same year

NEW! Time Traveler

Other Alcoholic Beverage Terms

finish, gimlet, mull, sake, setup, sommelier, syllabub, vintner, wassail

proof

verb

transitive verb

1 a : to make or take a proof or test of

b : proofread

2 : to give a resistant quality to

3 : to activate (yeast) by mixing with water and sometimes sugar or milk

—

proofer

noun

See proof defined for English-language learners

Examples of proof in a Sentence

She proofed the story carefully.

Recent Examples of proof from the Web

So now’s a good time for investors to bear-proof their 401(k)s before the next financial storm.

— matthew frankel, USA TODAY, "Ask a Fool: How much can I borrow from my retirement accounts?," 12 Apr. 2018
Elder-proofing your house San Diego County caregivers can request free or low-cost minor home modifications, such as the installation of hand rails, grab bars, smoke detectors and handheld shower heads, from at least three nonprofit organizations.

— michele parente, sandiegouniontribune.com, "Resources for dementia caregivers," 27 Apr. 2018
It’s more the collective sum of features that makes these, in my opinion, a more appealing product than the first pair of glasses; from their smaller frame to better components to water-proofing.

— lauren goode, WIRED, "Snapchat Debuts New Spectacles. We Try Them on for Size," 26 Apr. 2018
Since the deadly July 2016 flood in Ellicott City, Ron Peters has spent $150,000 on restoration and flood proofing measures to not only repair the damage, but protect his three properties in historic Ellicott City against floodwaters.

— kate magill, Columbia Flier, "For flood-prone Ellicott City, study lays out ideas to make buildings more ‘resilient’," 23 Mar. 2018
The reconstruction of the airport’s roof is expected to be completed this summer, which will be a critical step in water proofing the rest of the building and reopening the airport’s main building, Kartokromo said.

— chabeli herrera, miamiherald, "Two monster hurricanes battered these Caribbean islands. Now, they’re back in business | Miami Herald," 16 Apr. 2018
Letting the dough proof one more time encourages an airy texture.

— alex delany, Bon Appetit, "This Tax Season Stromboli Recipe Is My Only Dependent," 9 Apr. 2018
This video taken on a security camera during the 2011 Japanese earthquake shows why earthquake-proofing buildings is so important.

— sophie weiner, Popular Mechanics, "Watch This Earthquake-Proof Floor Survive a Disaster," 31 May 2017
Developments such as these are pre-emptive reforms made by savvy companies aimed at heading off a revolt, not proof that some revolution is underway in Hollywood, much less the wider world.

— alyssa rosenberg, chicagotribune.com, "'Ready Player One' seems like a celebration of fandom, but it's actually a dire warning," 1 Apr. 2018

First Known Use of proof

circa 1699

in the meaning defined at sense 1a

See Words from the same year

NEW! Time Traveler

Other Printing Terms

epigraph, errata, leader, mechanical, notch, tittle, underscore, widow

PROOF Defined for English Language Learners

proof

noun

: something which shows that something else is true or correct
: an act or process of showing that something is true
mathematics : a test which shows that a calculation is correct

proof

adjective

: designed or made to prevent or protect against something harmful

PROOF Defined for Kids

proof

noun \ ˈprüf \

1 : evidence of truth or correctness

“… Is there any clear proof … or is it mere hearsay?”
—Robert Lawson, Rabbit Hill

2 : a printing (as from type) prepared for study and correction

3 : a test print made from a photographic negative

4 : ¹test 2

Let's put her theory to the proof.

proof

adjective

: able to keep out something that could be harmful

The seal on the bottle is proof against tampering.

Hint: The adjective proof is usually used in compounds.

waterproof

Law Dictionary

proof

noun

1 : the effect of evidence sufficient to persuade a reasonable person that a particular fact exists — see also evidence

2 : the establishment or persuasion by evidence that a particular fact exists — see also burden of proof

3 : something (as evidence) that proves or tends to prove the existence of a particular fact — see also clear and convincing, preponderance of the evidence, reasonable doubt, standard of proof — compare allegation, argument

4 : probate 1a