proof

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.

• (UK, Canada) enPR: pro͞of, IPA^(key): /pɹuːf/
• (US) enPR: pro͞of, IPA^(key): /pɹuf/
• (General Australian, New Zealand) enPR: pro͞of, IPA^(key): /pɹʉːf/

• Audio (US)

  (file)

• Rhymes: -uːf

proof (countable and uncountable, plural proofs)

1. (countable) An effort, process, or operation designed to establish or discover a fact or truth; an act of testing; a test; a trial.
   • 1591, Edmund Spenser, Prosopopoia: or, Mother Hubbard's Tale, later also published in William Michael Rossetti, Humorous Poems,

     But the false Fox most kindly played his part,

     For whatsoever mother-wit or art

     Could work he put in proof. No practice sly,

     No counterpoint of cunning policy,

     No reach, no breach, that might him profit bring.

     But he the same did to his purpose wring.

   • c. 1633, John Ford, Love's Sacrifice, Act 1, Scene 1:

     France I more praise and love; you are, my lord,
     Yourself for horsemanship much famed; and there
     You shall have many proofs to shew your skill.

   • 1831, Thomas Thomson, A System of Chemistry of Inorganic Bodies, volume 2:

     A given quantity of the spirits was poured upon a quantity of gunpowder in a dish and set on fire. If at the end of the combustion, the gunpowder continued dry enough, it took fire and exploded; but if it had been wetted by the water in the spirits, the flame of the alcohol went out without setting the powder on fire. This was called the proof.

2. (uncountable) The degree of evidence which convinces the mind of any truth or fact, and produces belief; a test by facts or arguments which induce, or tend to induce, certainty of the judgment; conclusive evidence; demonstration.
   • c. 1603–1604 (date written), William Shakespeare, “The Tragedie of Othello, the Moore of Venice”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, (please specify the act number in uppercase Roman numerals, and the scene number in lowercase Roman numerals):

     I'll have some proof.

   • 1841, Ralph Waldo Emerson, “The Over-Soul”, in Essays: First Series:

     It was a grand sentence of Emanuel Swedenborg, which would alone indicate the greatness of that man's perception, — "It is no proof of a man's understanding to be able to confirm whatever he pleases; but to be able to discern that what is true is true, and that what is false is false, this is the mark and character of intelligence."

   • 1990 October 16, Paul Simon, “Proof”, in The Rhythm of the Saints, Warner Bros.:

     Faith, faith is an island in the setting sun
     But proof, yes
     Proof is the bottom line for everyone

3. The quality or state of having been proved or tried; firmness or hardness which resists impression, or does not yield to force; impenetrability of physical bodies.
4. (obsolete) Experience of something.
   • 1590, Edmund Spenser, “Book III, Canto I”, in The Faerie Queene. […], London: […] [John Wolfe] for William Ponsonbie, →OCLC:

     But the chaste damzell, that had never priefe / Of such malengine and fine forgerye, / Did easely beleeve her strong extremitye.

5. (uncountable, obsolete) Firmness of mind; stability not to be shaken.
6. (countable, printing) A proof sheet; a trial impression, as from type, taken for correction or examination.
   • 2010, Andrea Levy, The Long Song, Tinder Press (2017), page 382:

     And these men scour the printed proof for error, blunder, and misspelling.

7. (numismatics) A limited-run high-quality strike of a particular coin, originally as a test run, although nowadays mostly for collectors' sets.
8. (countable, logic, mathematics) A sequence of statements consisting of axioms, assumptions, statements already demonstrated in another proof, and statements that logically follow from previous statements in the sequence, and which concludes with a statement that is the object of the proof.
9. (countable, mathematics) A process for testing the accuracy of an operation performed. Compare prove, transitive verb, 5.
10. (obsolete) Armour of excellent or tried quality, and deemed impenetrable; properly, armour of proof.
    • c. 1606 (date written), William Shakespeare, “The Tragedie of Macbeth”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, →OCLC, (please specify the act number in uppercase Roman numerals, and the scene number in lowercase Roman numerals):

      Till that Bellona's bridegroom, lapped in proof

11. (US) A measure of the alcohol content of liquor. Originally, in Britain, 100 proof was defined as 57.1% by volume (no longer used). In the US, 100 proof means that the alcohol content is 50% of the total volume of the liquid; thus, absolute alcohol would be 200 proof.

• probe
• prove

• → Russian: пруф (pruf), пру́фы (prúfy)
  • ⇒ Russian: пруфли́нк (pruflínk, literally “proof + link”)

proof (comparative more proof, superlative most proof)

1. Used in proving or testing.

   a proof load; a proof charge

2. Firm or successful in resisting.

   proof against harm

   waterproof; bombproof

   • 1671, John Milton, “The Fourth Book”, in Paradise Regain’d. A Poem. In IV Books. To which is Added, Samson Agonistes, London: […] J. M[acock] for John Starkey […], →OCLC, page 130, lines 528–533:

     And opportunity I here have had / To try thee, ſift thee, and confeſs have found thee / Proof againſt all temptation as a rock / Of Adamant, and, as a Center, firm / To the utmoſt of meer man both wiſe and good, / Not more; […]

   • 1790, Edmund Burke, “Reflections on the Revolution in France”, in The Works of The Right Honourable Edmund Burke, volume 5, published 1803, page 426:

     This was a good, ſtout proof article of faith, pronounced under an anathema, by the venerable fathers of this philoſophick ſynod.

   • quoted in 1818, Christopher Kelly, History of the French Revolution and of the Wars produced by that Memorable Event

     The French cavalry, in proof armour, repeatedly charged our squares, their cannon opening chasms; but the British infantry, though greatly diminished, were inflexible and impenetrable to the last.

3. (of alcoholic liquors) Being of a certain standard as to alcohol content.

   60% proof liquor

proof (third-person singular simple present proofs, present participle proofing, simple past and past participle proofed)

1. (transitive, intransitive, colloquial) To proofread.
2. (transitive) To make resistant, especially to water.
3. (transitive, firearms) To test-fire with a load considerably more powerful than the firearm in question's rated maximum chamber pressure, in order to establish the firearm's ability to withstand pressures well in excess of those expected in service without bursting.
4. (transitive, cooking) To allow (yeast-containing dough) to rise.
5. (transitive, cooking) To test the activeness of (yeast).

• “proof”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.
• “proof”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.

• OPFOR