What does proof mean?
Proof means evidence or a convincing argument that establishes a fact. It can also refer to the ability of a person, material, or idea to withstand testing: something described as strong proof is considered capable of resisting challenge. In publishing, a proof is an early printed version used to check wording, spelling, and layout before the final copies are made. The related verb has two main uses. In an informal context, to proof something is to test it; in a technical or historical printing context, it is to check a proof or mark a document as ready for production. Although the word often suggests strong certainty, a proof may be merely the best available evidence, and the phrase “proof of concept” describes an early demonstration that a proposed system or idea can work rather than a final, fully developed result. In general use, proof is a formal and authoritative term associated with verification, demonstration, and established fact.
Evidence or an argument that establishes a fact or demonstrates that something is true.
"The witness gave strong proof that the document was genuine."
A formal and established term; often used in the phrase “proof of” to identify what is being demonstrated.
Resistant or proof against something.
"The container must be proof against moisture and damage during transport."
Chiefly used in the phrase “proof against,” especially in technical or product-related contexts.
To mark a document as ready for printing, or to test something.
"The editor will proof the pages before they are sent to the printer."
The testing sense is informal; the printing sense is specialized and historically common.
The plural is proofs. The sense referring to a printed impression or a mark also takes this plural form.
"The publisher corrected several errors in the proofs before the book went to press."
Before the age of digital documents, every printed page could be a proof: a chance to catch a misspelling while a mistake was still merely ink on paper.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does proof come from?
The word comes from Old English prof, meaning “a test, trial, or evidence,” related to the Old English verb profian, “to test, try, or prove.” The modern senses developed from the idea of examining something in order to establish its truth or quality. The word shares its root with prove, proven, and provable; the spelling with the double o reflects the historical form of the word.
Related word forms
How proof is actually used
In its standard noun sense, proof is formal and commonly used with of, such as “proof of identity.” As a verb, “to proof” is relatively informal in the sense of testing, while its printing-related use is more specialized. The adjective is chiefly used in the phrase “proof against.”
Easily confused with proof
A proof is evidence or an argument that establishes a fact, whereas to prove means to establish a fact or demonstrate something.
A proof is a printed impression used to check wording and appearance, whereas to proofread means to examine and correct writing before publication.