Noun

Singular proof

Plural proofs

proof (plural proofs)

1. Any 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. 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, William Shakespeare, The Tragedy of Othello, The Moor of Venice,

     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 doesn't yield to force; impenetrability of physical bodies.
4. Firmness of mind; stability not to be shaken.
5. (printing) A proof sheet; a trial impression, as from type, taken for correction or examination.
6. (mathematics): A process for testing the accuracy of an operation performed. Compare prove, transitive verb, 5.
7. (obsolete): Armour of excellent or tried quality, and deemed impenetrable; properly, armour of proof.
8. (US) A measure of the alcohol content of liquor. Originally, in Britain, 100 proof was defined as 57.1% by volume (not used anymore). In the US, 100 proof means that the alcohol content is 50% of the total volume of the liquid, and thus, absolute alcohol would be 200 proof.

Synonyms

• testimony
• evidence
• reason
• argument
• trial
• demonstration

Derived terms

• artist's proof
• burden of proof
• proof reader
• proof of concept

Related terms

• prove
• probe

Proof may refer to:

• Formal proof
• Mathematical proof
• Argument
• Proof theory, a branch of mathematical logic that represents proofs as formal mathematical objects
• Justification, in epistemology, a reason for or explanation of a proposition or belief
• Provability logic
• Evidence, information which tends to determine or demonstrate the truth of a proposition
• Evidence (law), tested evidence or a legal proof
• Proofing (baking technique), the process by which a yeast-leavened dough rises, also called "proving"
• Recursively enumerable set also know as a provable set

Various kinds of testing, checking, or measuring:

• Proofreading, reviewing a manuscript or artwork for errors or improvements
• Prepress proof, a facsimile of press artwork for job verification
• Artist's proof, a single print taken during the printmaking process
• Proof coinage, a coin made as an example of a particular strike
• Proof test, for a firearm
• Homeopathic proving, a homeopathic procedure
• Galley proof, a preliminary version of a publication
• Alcoholic proof, a measure of an alcoholic drink's strength
• Proof procedure
• Proof complexity

In entertainment:

• Proof (TV series) (2004 and 2005), an Irish TV drama/thriller, co-produced by RTÉ and TV 2 (Denmark)
• Proof (1991 film), an Australian film by Jocelyn Moorhouse
• Proof (play), a play by David Auburn
• Proof (2005 film), a film directed by John Madden, based on the play
• "Proof", a B-side by the band Coldplay, off their single "Speed of Sound"
• "Proof", a song by Paul Simon from his 1990 album The Rhythm of the Saints
• "Proof", a song by Happy Rhodes from her 1998 album Many Worlds Are Born Tonight
• "Proof", a 2004 song by J-pop group angela
• "Proof", a 2007 song by Japanese artist Mell
• Proof (rapper) (1973–2006), American rapper and member of D12
• Proof (comics), a comic series from Image Comics