English Reference
noun · adjective · verb

proof

n. · adj. · v.
US /ˈpɹuf/ UK /pɹˈuːf/ proof UK spelling proof's, proof's, proofed

  1. 01 B1 Intermediate

    n.information or evidence that shows something is definitely true.

    n.conclusive evidence or a body of facts that establishes the validity of a statement or the truth of a fact.

    Simple

    The police found a video that provided clear proof of his innocence.

    In context

    The prosecution struggled to provide definitive proof of the defendant's involvement, as most of the forensic evidence had been contaminated at the scene.

    Pitfall
    I have many proofs that he is lying. I have proof that he is lying.

    In the sense of general evidence, 'proof' is usually uncountable. Use 'pieces of proof' or just 'proof' instead of the plural 'proofs'.

    disproofrefutation
  2. 02 B2 Upper Intermediate Academic Math

    n.a series of logical steps used to show that a math rule is true.

    n.a formal sequence of logical steps, starting from axioms, that demonstrates the truth of a mathematical or logical proposition.

    Simple

    The teacher asked the students to write a proof for the geometry problem.

    In context

    The mathematician spent years developing a rigorous proof for the theorem, which had remained unverified for over a century.

  3. 03 C1 Advanced Technical

    n.a trial copy of a document or photo used to check for mistakes before the final version is printed.

    n.a preliminary version of a printed piece, such as a page or photograph, produced for review and correction before the final production run.

    Simple

    The author spent the afternoon checking the page proofs for spelling errors.

    In context

    Before the magazine went to press, the editor insisted on reviewing the colour proofs to ensure the photography was reproduced accurately.

    trial printdraft
  4. 04 C2 Proficiency American EnglishTechnical

    n.a measurement of how much alcohol is in a drink.

    n.a measure of the ethanol content in an alcoholic beverage, traditionally defined in the US as twice the percentage of alcohol by volume.

    Simple

    This whiskey is 80 proof, which means it contains 40 percent alcohol.

    In context

    The distillery produced a high-proof spirit intended specifically for blending, rather than for direct consumption.

  5. 05 B2 Upper Intermediate

    adj.able to resist or protect against something, like water or fire.

    adj.impervious or resistant to a specific damaging agent; often used as a suffix in compound words.

    Simple

    No system is completely proof against hackers if they are determined enough.

    In context

    The bunker was designed to be proof against even the most powerful conventional explosives available at the time.

    Usage

    Usually follows the noun it modifies or functions as a suffix, as in 'waterproof' or 'bulletproof'.

  6. 06 C1 Advanced Technical

    v.to treat something so that it is protected from things like water.

    v.to treat a surface or material with a substance that makes it resistant to a specific external force or element.

    Simple

    You should proof your boots with a special spray before going hiking in the rain.

    In context

    The contractor recommended that we proof the exterior masonry to prevent moisture from seeping into the structural timber during the winter months.

  7. 07 C1 Advanced Technical Cooking

    v.to let bread dough rise before baking it.

    v.to allow yeast-leavened dough to rise, typically after shaping, to achieve the desired volume and texture before baking.

    Simple

    Let the rolls proof in a warm place for about an hour until they double in size.

    In context

    If you fail to proof the dough sufficiently, the resulting loaf will be dense and lack the airy crumb characteristic of a well-made sourdough.

    riseleaven
  8. 08 B2 Upper Intermediate Informal

    v.to read through a text to find and fix mistakes.

    v.to read and mark corrections in a manuscript or printed proof.

    Simple

    Could you proof this email for me before I send it to the boss?

    In context

    The intern was tasked to proof the final draft of the annual report, ensuring that all financial figures aligned with the provided spreadsheets.

    proofreadeditcorrect

Usage proof of concept

The evidence will need to include proof it was marketed for sale for at least 12 months.

BBC News· 16 Aug 2026

That’s proof there is no wrong door, only different routes that suit everyone’s individual ambition.

The Guardian· 20 Aug 2026

From Middle English proof, from Old French prove, from Late Latin proba (“a proof”), from Latin probō (“to prove”); see prove; compare also the doublet probe.

Etymology adapted from Wiktionary, available under CC BY-SA 4.0.

This entry
Origin Latin probō
Level B2 · Upper Intermediate
Frequency Common
Updated