Definition of proof
(Entry 1 of 3)
1a : 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
3 : something that induces certainty or establishes validity
4 archaic : the quality or state of having been tested or tried especially : unyielding hardness
5 : evidence operating to determine the finding or judgment of a tribunal
6a 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 : a test applied to articles or substances to determine whether they are of standard or satisfactory quality
8a : 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
proof
adjectiveDefinition of proof (Entry 2 of 3)
1 : able to resist or repel
boots that were … proof against cold and wet— Robertson Davies —often used in combinationwindproof
2 : used in proving or testing or as a standard of comparison
3 : of standard strength or quality or alcoholic content
proof
verbproofed; proofing; proofs
Definition of proof (Entry 3 of 3)
1a : to make or take a proof or test of
b : proofread
2 : to give a resistant quality to
3 : to activate (yeast) by mixing with water and sometimes sugar or milk
Keep scrolling for more
Keep scrolling for more
Keep scrolling for more
Keep scrolling for more
Test Your Vocabulary
Words of Snow and Ice Quiz
- Which of the following refers to thin, bending ice, or to the act of running over such ice?

Test your knowledge - and maybe learn something along the way.
TAKE THE QUIZ
Anagram puzzles meet word search.
TAKE THE QUIZLove words? Need even more definitions?
Merriam-Webster unabridgedWords at Play
Ask the Editors
Word Games
Words of Snow and Ice Quiz
A selection of words from the chillier parts of t...
Take the quizName that Thing: Toys and Games Edition
It's all fun and games until someone beats your h...
Take the quizTrue or False?
Test your knowledge - and maybe learn something a...
Take the quizSCRABBLE® Sprint
SCRABBLE® fans, sharpen your skills!
Play the game
Share proof
Time Traveler for proof
The first known use of proof was in the 13th century
See more words from the same century