proof

¹ American  

[proof] / pruf /

noun

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)

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  

adjective

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

   waterproof

   mothproof

   childproof

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proof ² 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 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.”

Related Words

See evidence.

Other Word Forms

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

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”; 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

The proof of whether it is "business as usual", as O'Neil suggested, will be seen when the Mexico event gets under way on Thursday.

From BBC • Apr. 16, 2026

These laws usually require proof of citizenship in the form of a passport or birth certificate — documents that are difficult for many Americans to access or obtain.

From Salon • Apr. 16, 2026

Researchers emphasize that the findings show an association, not proof that lifelong learning directly prevents Alzheimer's.

From Science Daily • Apr. 15, 2026

An hour passes, but we’re all determined to take a piece of this day home — more than a memento, but proof that we were a part of it.

From Los Angeles Times • Apr. 14, 2026

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

From "American Spirits" by Barb Rosenstock

Related Words

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