proof

/pɹuːf/

//pɹuːf// noun

By · According to Wiktionary data (CC BY-SA) ·

"proof" is a 5-letter English headword indexed on PlainSpell.

The verdict

“proof” is a regularly-used English word, ranked #2,052 in English word frequency and used as a noun.

#2,052
frequency rank, English
5
letters
7
tracked misspellings
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed May 6, 2026) - An effort, process, or operation designed to establish or discover a fact or truth; an act of testing; a test; a trial.

Visual similarity to commonly confused words

How many letter changes separate each confused pair (Levenshtein distance, normalized).

proof vs pros
60% similar
proof vs prop
60% similar
proof vs Prot
40% similar

Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).

Key facts for proof
PropertyValue
Headwordproof
LanguageEnglish
Part of speechNoun
IPA/pɹuːf/
Letters5
Frequency rank#2,052
Misspellings tracked7
Confusable pairs20
SourceWiktionary (kaikki.org)

Where “proof” sits in English frequency

Every-word frequency runs from the handful of words we use constantly (left) to the long tail used once in a blue moon (right). proof lands here:

#1#100#1K#10K#100K
← used constantlyrarely used →

Scale is logarithmic (each tick is 10× rarer). Source: FrequencyWords open word-frequency list.

Spelling & Dictionary Insight

The English entry for proof is 5 letters long, classified as a noun, and transcribed in the International Phonetic Alphabet as /pɹuːf/. Corpus data places it at rank #2,052 in overall English word frequency, indicating it appears regularly in written and spoken text. Wiktionary records 11 distinct senses for this headword, so context determines which meaning a reader should apply.

Our generated misspelling index lists 7 likely wrong-spelling variants for proof, with forms such as "porof", "pproof", and "prof". Each of these forms differs from the correct spelling by one small edit: a doubled letter, a dropped silent letter, or a substituted vowel. It also participates in 20 confusable-pair relationships, "pros", "prop", "Prot", and more, a pairing that trips writers up because the two words share enough sound or shape to blur together.

Etymologically, the entry records: 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. The correct English form is proof, spelled P-R-O-O-F.

Definition

  1. 1
    An effort, process, or operation designed to establish or discover a fact or truth; an act of testing; a test; a trial.
  2. 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.
  3. 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. 4
    Experience of something.
  5. 5
    Firmness of mind; stability not to be shaken.
  6. 6
    A proof sheet; a trial impression, as from type, taken for correction or examination.
  7. 7
    A limited-run high-quality strike of a particular coin, originally as a test run, although nowadays mostly for collectors' sets.
  8. 8
    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. 9
    A process for testing the accuracy of an operation performed. Compare prove, transitive verb, 5.
  10. 10
    Armour of excellent or tried quality, and deemed impenetrable; properly, armour of proof.
  11. 11
    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, perfectly pure absolute alcohol would be 200 proof.

Etymology

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.

This word in other languages

prueba(Español)preuve(Français)Beweis(Deutsch)

Common misspellings

Also misspelled as: porof,pproof,prof,profo,prooff,prroof,rpoof

Misspelling Pattern Breakdown

How far each generated variant is from the correct spelling of proof - counted as single-character edits (an insertion, a deletion, or a substituted letter). The larger the bar, the easier the typo is to spot; one-edit slips are the ones that sneak past readers.

porof2pproof1prof1profo2prooff1prroof1rpoof2
Edit distance from "proof"

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "proof"?
"proof" is spelled P-R-O-O-F. The IPA pronunciation is /pɹuːf/.
What does "proof" mean?
As a noun, "proof" means: An effort, process, or operation designed to establish or discover a fact or truth; an act of testing; a test; a trial.
What words are commonly confused with "proof"?
"proof" is commonly confused with "pros", "prop", "Prot". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "proof"?
The IPA (International Phonetic Alphabet) transcription for "proof" is /pɹuːf/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "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. See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Using “proof”

The practical upshot for anyone who landed here from a spell-check.

  • The one correct English spelling is P-R-O-O-F - every other letter order is a misspelling in standard orthography.
  • Say it as /pɹuːf/ (IPA); tap the speaker on the pronunciation badge to hear it where audio exists.
  • Don't mix it up with “pros” - see the side-by-side comparison. proof vs pros
  • Browse more English words and confusable pairs in the same reference. English words
Data Source

Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list FrequencyWords open word-frequency list