proof

1 of 3

noun

ˈprüf 

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

proof

2 of 3

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

proof

3 of 3

verb

proofed; proofing; proofs

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

Synonyms

Noun

• evidence
• testimony
• documentation

Examples of proof in a Sentence

Noun

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.

Verb

She proofed the story carefully.

Recent Examples on the Web

Noun

Those seeking renewal permits will also have to show proof of training from a verified instructor within 6 months of their renewal application. —Barnini Chakraborty, The Washington Examiner, 22 June 2025

That is not entirely fair — Liverpool submitted a £110m bid for Brighton’s Moises Caicedo in the summer of 2023, only for the Ecuadorian to choose Chelsea instead, which Anfield executives often cite as proof of the club’s readiness to pay top dollar for the right player. —Gregg Evans, New York Times, 20 June 2025

Adjective

The test site is currently the only place where SpaceX can put Starships through proof testing and static fire tests before declaring the rockets are ready to fly. —ArsTechnica, 19 June 2025

Christensen’s unique trick is also proof that a makeup product doesn’t have to just be used for its singular, intended purpose, which reminds us of Salma Hayek’s hack for covering gray hairs. —Izzy Baskette, People.com, 18 June 2025

Verb

By encouraging and enabling others to grow, take risks, and fuel innovation, business leaders are not only driving greater engagement and performance, but also future proofing their organization for years to come. —Sasha Rogelberg, Fortune, 18 June 2025

Hosseini countered that Ono’s evolving view on DEI was not a compromise of conservative values but instead proof that Florida’s approach to higher education is resonating across the country. —Steven Walker, The Orlando Sentinel, 3 June 2025

Word History

Etymology

Noun

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

First Known Use

Noun

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

Adjective

1583, in the meaning defined at sense 1

Verb

circa 1699, in the meaning defined at sense 1a

Phrases Containing proof

• burden of proof
• living proof
• proof of concept
• proof of purchase
• proof positive
• proof spirit
• reproduction proof
• the proof is in the pudding
• the proof of the pudding is in the eating
• veto-proof

Rhymes for proof

• goof
• hoof
• kloof
• poof
• roof
• spoof
• woof
• aloof
• behoof
• disproof
• flameproof
• foolproof

Kids Definition

proof

1 of 3 noun

ˈprüf 

1

a

: evidence of truth or correctness

gave proof of her statement

b

: an act or process of showing or finding out that something is true especially by reasoning or by experiment

a proof that the theorem is true

put a theory to the proof

2

a

: a copy (as of something set in type) taken for study and correction

b

: a test print made from a photographic negative

proof

2 of 3 adjective

: designed or made to prevent or keep out something that could be harmful

this lock is proof against tampering

—often used in compounds

waterproof

proof

3 of 3 verb

: to activate (yeast) by mixing with water

Legal Definition

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 sense 1a

Etymology

Noun

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