\ˈprüf \

Definition of proof 

(Entry 1 of 3)

1a : 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

6a 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

8a : 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



Definition of proof (Entry 2 of 3)

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


proofed; proofing; proofs

Definition of proof (Entry 3 of 3)

transitive verb

1a : 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

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Other Words from proof


proofer noun

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.


She proofed the story carefully.
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Recent Examples on the Web: Noun

The scar, a little crescent hollow in the ring finger of my right hand, is the only proof. Rawiya Kameir, Vogue, "Does Citizenship Shape Identity? A “Third-Culture” Writer Takes Stock," 19 Oct. 2018 To some, this is definitive proof that Bigfoot is as real as mountain gorillas or narwhals. Matt Blitz, Popular Mechanics, "Science Meets Legend: The Story of Our Search for Bigfoot," 8 Oct. 2018 But this is just further proof of Fashion Nova's commitment to court the Insta generation. Krystin Arneson, Glamour, "Fashion Nova Already Knocked Off Looks From Kylie Jenner's Birthday Party," 11 Aug. 2018 In a proof-of-life video after their kidnapping, the three men had identified their captors as members of a dissident arm of the now disbanded Revolutionary Armed Forces of Colombia. Fox News, "Bodies of 3 kidnapped Ecuadorean press workers identified," 25 June 2018 Researchers also found bones of pigs and deer, but were not able to provide proof that the tools were used for hunting. Time, "A Discovery in China Suggests That Human-Like Species Left Africa 250,000 Years Earlier Than Believed," 13 July 2018 Skeptics believe that extraordinary claims, from claims of aliens to government aircraft that can make abrupt 90 degree turns in violation of the laws of physics, require extraordinary proof. Kyle Mizokami, Popular Mechanics, "70 Years and Counting, the UFO Phenomenon Is as Mysterious As Ever," 2 July 2018 Military discounts Participation can vary by location and proof of military service is usually required. Kelly Tyko, ajc, "Oorah! Where active military, vets can save on Independence Day," 1 July 2018 Amanda Clark Palmer: There is zero proof that Victoria Rickman invited Will Carter to her house. Erin Moriarty, CBS News, "Was alleged rape and shooting death investigation influenced by reality TV cameras?," 30 June 2018

Recent Examples on the Web: Adjective

Historically, Senate rules required a filibuster-proof coalition of 60 votes in order to confirm a Supreme Court hopeful. Jay Willis, GQ, "Why Justice Kennedy’s Retirement Is Even Worse Than You Think," 27 June 2018 Myers' husband called Fish and Game and put what remained of the family's livestock in a bear-proof dumpster. Tegan Hanlon, Anchorage Daily News, "Brown bear killed in Chugiak after it attacked 22 chickens and a goat," 2 May 2018 Acceptable deposits include prescription medications, over-the-counter medicine, and pet medicine, in pills, capsules, inhalers, ointments, patches, and liquids in leak-proof containers. Margeaux Sippell,, "Boston residents urged to drop off old medications Saturday," 27 Apr. 2018 Make sure food is in mouse-proof containers, for one. NBC News, "New York City mice are loaded with bacteria, superbug germs," 17 Apr. 2018 This can be made ahead of time and refrigerated in an air proof container. Nina Mandell, For The Win, "11 ridiculously easy and delicious last-minute Super Bowl recipes," 2 Feb. 2018 Pruitt had faced increasing public criticism and ethics reviews in recent months as expenses over security measures, first-class flights and a sound-proof communications system came to light. Ledyard King, USA TODAY, "Trump EPA chief Scott Pruitt resigns as ethical scandals mount," 5 July 2018 If that tweet isn’t proof enough, just look at his decision to enter the draft in the first place. Chapel Fowler, charlotteobserver, "If Panthers rookie DT Kendrick Norton makes roster, he's still 31 steps short of goal," 7 June 2018 If the martial problems of those close to Trump isn’t proof enough of his toxicity, then the ability to reconcile after being pushed away from him is. Adam K. Raymond, Daily Intelligencer, "Within Trump’s Orbit, Divorce Is the Hot New Trend," 5 Apr. 2018

Recent Examples on the Web: Verb

Theater people have the best advice on sweat-proofing makeup Who among us hasn’t pirouetted all night (literally or figuratively) and felt their foundation start to slide off? Jamie Beckman, Allure, "Backstage Beauty Secrets From the Cast and Crew of Hamilton and Sleep No More," 13 Aug. 2018 Even tiny cracks in the weather-proofing around cables can allow water molecules to embed in the strands and attenuate the signal. Rob Goodier, Popular Mechanics, "How Climate Change Could Break the Internet," 19 July 2018 Check out how to get rid of as much dust in your home as possible, along with how to pollen-proof your place. Korin Miller, SELF, "What’s an Asthma Exacerbation? (Because It Sounds Really Scary.)," 11 July 2018 Never has the drama of a proofing drawer felt more alive and essential. Margaret Lyons, New York Times, "How Much Watching Time Do You Have This Weekend?," 21 June 2018 The two men proofed each other’s papers, talked about assignments, took turns at an improvised desk in the cell with a toilet seat as the chair. Nick Anderson, Washington Post, "‘Could I make it in college?’: His journey to a bachelor’s degree started behind bars," 24 May 2018 Sky would play an important role in both Disney’s and Comcast’s future-proofing efforts., "UK clears way for bidding war between Comcast and Disney over Sky," 5 June 2018 Stopping their spread is really contingent on doing other things like pollen-proofing your home or designating your room as a no-pet zone. Nina Bahadur, SELF, "How Does Allergy-Proof Bedding Actually Work?," 8 June 2018 In order for an animal to qualify, the passenger must provide a letter from a mental-health professional describing the mental or emotional disability that shows the need for the animal, and proof the professional’s licensing. Bart Jansen, USA TODAY, "American tightens leash on comfort animals flying with passengers, following Delta and United," 14 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.

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First Known Use of proof


13th century, in the meaning defined at sense 1a


1583, in the meaning defined at sense 1


circa 1699, in the meaning defined at sense 1a

History and Etymology for proof


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

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Statistics for proof

Last Updated

12 Nov 2018

Look-up Popularity

Time Traveler for proof

The first known use of proof was in the 13th century

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More Definitions for proof



English Language Learners Definition of proof

 (Entry 1 of 2)

: 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



English Language Learners Definition of proof (Entry 2 of 2)

: designed or made to prevent or protect against something harmful


\ˈprüf \

Kids Definition of proof

 (Entry 1 of 2)

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 : test entry 1 sense 2 Let's put her theory to the proof.



Kids Definition of proof (Entry 2 of 2)

: 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



Legal Definition of proof 

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

History and Etymology for proof

alteration of Middle English preove, from Old French preuve, from Late Latin proba, from Latin probare to prove

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Comments on proof

What made you want to look up proof? Please tell us where you read or heard it (including the quote, if possible).


noxious or harmful

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