Merriam-Webster Logo
  • Dictionary
  • Thesaurus
  • Medical
  • Scrabble
  • Spanish Central
  • Learner's Dictionary


noun \ˈprüf\

Simple Definition of proof

  • : 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

Full Definition of proof

  1. 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. 2 obsolete :  experience

  3. 3 :  something that induces certainty or establishes validity

  4. 4 archaic :  the quality or state of having been tested or tried; especially :  unyielding hardness

  5. 5 :  evidence operating to determine the finding or judgment of a tribunal

  6. 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. 7 :  a test applied to articles or substances to determine whether they are of standard or satisfactory quality

  8. 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>

Examples of proof

  1. The document was proof that her story was true.

  2. He claims that he was home when the murder was committed, but he has no proof.

  3. The proof shows that the theorem is true.

Origin of proof

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: 13th century

Rhymes with proof




Simple Definition of proof

  • : designed or made to prevent or protect against something harmful

Full Definition of proof

  1. 1 :  able to resist or repel <boots that were…proof against cold and wet — Robertson Davies> —often used in combination <windproof>

  2. 2 :  used in proving or testing or as a standard of comparison

  3. 3 :  of standard strength or quality or alcoholic content


First Known Use of proof


Other Alcoholic Beverage Terms




Definition of proof

  1. transitive verb
  2. 1 a :  to make or take a proof or test of b :  proofread

  3. 2 :  to give a resistant quality to

  4. 3 :  to activate (yeast) by mixing with water and sometimes sugar or milk

proof·er noun

Examples of proof

  1. She proofed the story carefully.


First Known Use of proof


Seen and Heard

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


February 12, 2016

of, relating to, or suggestive of marble

Get Word of the Day daily email!


Take a 3-minute break and test your skills!


How much does a batman (the Turkish unit of measurement) weigh?

100 pounds 2.2 pounds 16.96 pounds 196.5 pounds
Name That Thing

10 quick questions: hear them, spell them, and see how your skills compare to the crowd.


Test Your Knowledge - and learn some interesting things along the way.