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• proof
  proof

  noun

  evidence sufficient to establish a thing as true, or to produce belief in its truth.
• -proof
  -proof

  a combining form meaning “resistant, impervious to” that specified by the initial element.

proof

¹ American  

[proof] / pruf /

noun

• proofs
  plural

1. evidence sufficient to establish a thing as true, or to produce belief in its truth.

   Synonyms:

   support, corroboration, demonstration, confirmation

2. anything serving as such evidence.

   What proof do you have?

3. the act of testing or making trial of anything; test; trial.

   to put a thing to the proof.

   Synonyms:

   assay, examination

4. the establishment of the truth of anything; demonstration.

5. Law. (in judicial proceedings) evidence having probative weight.

6. the effect of evidence in convincing the mind.

7. an arithmetical operation serving to check the correctness of a calculation.

8. Mathematics, Logic. a sequence of steps, statements, or demonstrations that leads to a valid conclusion.

9. a test to determine the quality, durability, etc., of materials used in manufacture.

10. Distilling.

    1. the arbitrary standard strength, as of an alcoholic liquor.

    2. strength with reference to this standard: “100 proof ” signifies a proof spirit, usually 50% alcohol.

11. Photography. a trial print from a negative.

12. Printing.

    1. a trial impression, as of composed type, taken to correct errors and make alterations.

    2. one of a number of early and superior impressions taken before the printing of the ordinary issue.

       to pull a proof.

13. (in printmaking) an impression taken from a plate or the like to show the quality or condition of work during the process of execution; a print pulled for examination while working on a plate, block, stone, etc.

14. Numismatics. one of a limited number of coins of a new issue struck from polished dies on a blank having a polished or matte surface.

15. the state of having been tested and approved.

16. proved strength, as of armor.

17. Scots Law. the trial of a case by a judge alone, without a jury.

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adjective

1. able to withstand; successful in not being overcome.

   proof against temptation.

   Synonyms:

   steadfast, firm

2. impenetrable, impervious, or invulnerable.

   proof against outside temperature changes.

3. used for testing or proving; serving as proof.

4. of standard strength, as an alcoholic liquor.

5. of tested or proven strength or quality.

   proof armor.

6. noting pieces of pure gold and silver that the U.S. assay and mint offices use as standards.

verb (used with object)

• proofs,
  present (3rd person singular)
• proofed,
  past participle,  past
• proofing
  present participle

1. to test; examine for flaws, errors, etc.; check against a standard or standards.

2. Printing. prove.

3. to proofread.

4. to treat or coat for the purpose of rendering resistant to deterioration, damage, etc. (often used in combination).

   to proof a house against termites; to shrink-proof a shirt.

5. Cooking.

   1. to test the effectiveness of (yeast), as by combining with warm water so that a bubbling action occurs.

   2. to cause (especially bread dough) to rise due to the addition of baker's yeast or other leavening.

-proof ² American  

1. a combining form meaning “resistant, impervious to” that specified by the initial element.

   burglarproof; childproof; waterproof.

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proof ¹ British  

/ pruːf /

noun

1. any evidence that establishes or helps to establish the truth, validity, quality, etc, of something

2. law the whole body of evidence upon which the verdict of a court is based

3. maths logic a sequence of steps or statements that establishes the truth of a proposition See also direct induction induction

4. the act of testing the truth of something (esp in the phrase put to the proof )

5. Scots law trial before a judge without a jury

6. printing a trial impression made from composed type, or a print-out (from a laser printer, etc) for the correction of errors

7. (in engraving, etc) a print made by an artist or under his supervision for his own satisfaction before he hands the plate over to a professional printer

8. photog a trial print from a negative

9. 1. the alcoholic strength of proof spirit

   2. the strength of a beverage or other alcoholic liquor as measured on a scale in which the strength of proof spirit is 100 degrees

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adjective

1. able to resist; impervious (to)

   the roof is proof against rain

2. having the alcoholic strength of proof spirit

3. of proved strength or impenetrability

   proof armour

verb

1. (tr) to take a proof from (type matter, a plate, etc)

2. to proofread (text) or inspect (a print, etc), as for approval

3. to render (something) proof, esp to waterproof

-proof ² British  

adjective

1. secure against (damage by); (make) impervious to

   waterproof

   mothproof

   childproof

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proof Scientific  

/ pro̅o̅f /

1. A demonstration of the truth of a mathematical or logical statement, based on axioms and theorems derived from those axioms.

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Usage

What does -proof mean? The combining form -proof is used like a suffix meaning “resistant, impervious to.” Impervious means "impenetrable." It is occasionally used in a variety of everyday and technical terms. The form -proof ultimately comes from Latin proba, meaning “test.”

Synonym Usage

See evidence.

Other Word Forms

Derived Forms

• re-proof
  verb (used with object)
• unproofed
  adjective

Inflected Forms

Nouns

• proofs
  plural

Participles

• proofing
  present
• proofed
  past

Conjugated Forms

Present

• proof
  simple
• proofs
  simple
• have proofed
  perfect
• has proofed
  perfect
• am proofing
  progressive
• are proofing
  progressive
• is proofing
  progressive
• have been proofing
  perfect progressive
• has been proofing
  perfect progressive

Past

• proofed
  simple
• had proofed
  perfect
• was proofing
  progressive
• were proofing
  progressive
• had been proofing
  perfect progressive

Future

• will proof
  simple
• will have proofed
  perfect
• will be proofing
  progressive
• will have been proofing
  perfect progressive

Etymology

Origin of proof

First recorded in 1175–1225; Middle English prove, prooff, prof, proufe, alteration (by association with the vowel of prove ) of preove, proeve, prieve, pref, from Middle French preve, proeve, prueve, from Late Latin proba “a test,” akin to Latin probāre “to test and find good”; cf. pree

Explanation

Proof is the evidence that shows something is true or valid. When you show the logical steps that take you from your hypothesis that the world is round to the conclusion that it is, you're formulating a proof. Photographic prints that haven't been touched up are also called proofs, and that’s also what you call the first copy of a printed text, before it's checked for errors and corrected. When you check a text for errors, you're proofing. If your poker strategy is foolproof, even somebody who knows nothing about poker — a poker fool, that is — can’t get it wrong. Proof is a word you’ll see on bottles of alcohol, too: 90-proof rum means it's 45% alcohol.

Example Sentences

See Examples For:

proof -proof proofs proofed proofing

Did I have proof my Reddit handle was actually connected to who I said I was?

From Slate ● Oct. 11, 2026

His films will one day too become flowers left not only as proof of his time on earth, but perhaps as messages for those to come who have the sensibility to appreciate them.

From Los Angeles Times ● Oct. 9, 2026

But more than anything, Urschel is a math guy now—his latest proof is proof.

From The Wall Street Journal ● Oct. 8, 2026

The immune findings are intriguing, but they should not be interpreted as proof that taking D3 will prevent a particular infection.

From Science Daily ● Oct. 8, 2026

No more swinging, slapping, or bed-destroying; just gentle rapping, proof of an afterlife.

From "American Spirits" by Barb Rosenstock

Hotel managers learned that, despite jokes about -proof industries, relying heavily on a Western male clientele was unwise at a time when the United States and Europe were buffeted by recession.

From New York Times ● Sep. 16, 2010

"To be clear, we did not use their prompts or proofs to prompt our models or direct our agents," Bubeck said.

From Barron's ● Sep. 8, 2026

"However, our proofs differ significantly and even the precise results proved are different."

From BBC ● Sep. 8, 2026

This suggests AI may prove to be just as valuable for discovering unexpected mathematical objects as it is for constructing proofs.

From Science Daily ● Aug. 6, 2026

“It’s fair to say that we haven’t seen yet the spark of genius that you could attribute to some of the grandest proofs in the history of humanity,” Bubeck told me.

From The Wall Street Journal ● May 30, 2026

I would assure him that I would try not to, and that in any event he would be checking the manuscript page by page, and ultimately the galley proofs.

From "The Autobiography of Malcolm X" by Alex Malcolm X;Hailey

Campbell ran Ben’s Bread solo for six of the last eight years, sometimes speeding between multiple kitchens across the city to get everything proofed, baked and packaged.

From Seattle Times ● Jun. 22, 2023

He wants to see the new law "contain future proofed regulation", so it also requires the same admission for altered videos, and any other tech developments.

From BBC ● May 14, 2023

Tip the proofed dough out to the center of the parchment paper so the seam is facing down.

From Salon ● Apr. 14, 2022

Apparently, the host explained that she had "stupid proofed" the room – not just by using the notes but also making hardware adjustments.

From Fox News ● Dec. 21, 2021

There was not a piece of armour proofed in Europe but what Unde Dap had a theory about it He was furious with the new Gothic style, with its ridges and scallop-patterns and fluting.

From "The Once and Future King" by T. H. White

Existing state law requires landlords to maintain certain “standard characteristics” for a dwelling unit including adequate hot and cold running water, heat, and weather proofing.

From Los Angeles Times ● Oct. 8, 2025

The Barrett campaign described this as a simple proofing screw-up and said that the team had been working off of a template used ahead of the state’s Aug. 6 primary.

From Slate ● Oct. 19, 2024

Got a bread baker on your gift list? Etsy.com has sellers of personalized loaf pans; proofing and baking kits; patterned linen bread bags; and handmade baskets and crockery.

From Washington Times ● Nov. 15, 2023

This includes damp proofing, improving loft insulation and repairing the roof.

From BBC ● Jun. 30, 2023

The only similarity between the rest of the town and the church is the small windows covered with iron bars, but the shambler proofing is barely noticeable on such an impressive building.

From "Dread Nation" by Justina Ireland

Related Words

• argument
• clue
• confirmation
• criterion
• data
• demonstration
• information
• picture
• reason
• testament
• testimony
• validation
• verification