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List of logic symbols

From Wikipedia, the free encyclopedia

In logic, a set of symbols is commonly used to express logical representation. The following table lists many common symbols, together with their name, pronunciation, and the related field of mathematics. Additionally, the third column contains an informal definition, the fourth column gives a short example, the fifth and sixth give the Unicode location and name for use in HTML documents.[1] The last column provides the LaTeX symbol.

Basic logic symbols

Symbol Name Read as Category Explanation Examples Unicode

material implication implies; if ... then propositional logic, Heyting algebra is false when is true and is false but true otherwise.[2][circular reference]

may mean the same as (the symbol may also indicate the domain and codomain of a function; see table of mathematical symbols).

may mean the same as (the symbol may also mean superset).
is true, but is in general false (since could be −2). U+21D2



\to or \rightarrow

material equivalence if and only if; iff; means the same as propositional logic is true only if both and are false, or both and are true. U+21D4



negation not propositional logic The statement is true if and only if is false.

A slash placed through another operator is the same as placed in front.







\lnot or \neg


Domain of discourse Domain of predicate Predicate (mathematical logic) U+1D53B 𝔻 𝔻 \mathbb{D}

logical conjunction and propositional logic, Boolean algebra The statement AB is true if A and B are both true; otherwise, it is false. n < 4  ∧  n >2  ⇔  n = 3 when n is a natural number. U+2227






\wedge or \land
\cdot \&[3]

logical (inclusive) disjunction or propositional logic, Boolean algebra The statement AB is true if A or B (or both) are true; if both are false, the statement is false. n ≥ 4  ∨  n ≤ 2  ⇔ n ≠ 3 when n is a natural number. U+2228





\lor or \vee


exclusive disjunction xor; either ... or propositional logic, Boolean algebra The statement AB is true when either A or B, but not both, are true. AB means the same. A) ⊕ A is always true, and AA always false, if vacuous truth is excluded. U+2295






Tautology top, truth propositional logic, Boolean algebra The statement is unconditionally true. ⊤(A) ⇒ A is always true. U+22A4


Contradiction bottom, falsum, falsity propositional logic, Boolean algebra The statement ⊥ is unconditionally false. (The symbol ⊥ may also refer to perpendicular lines.) ⊥(A) ⇒ A is always false. U+22A5


universal quantification for all; for any; for each first-order logic ∀ xP(x) or (xP(x) means P(x) is true for all x. U+2200

existential quantification there exists first-order logic ∃ x: P(x) means there is at least one x such that P(x) is true. n is even. U+2203 \exists
uniqueness quantification there exists exactly one first-order logic ∃! x: P(x) means there is exactly one x such that P(x) is true. U+2203 U+0021 ∃ ! ∃! \exists !

definition is defined as everywhere x ≔ y or x ≡ y means x is defined to be another name for y (but note that ≡ can also mean other things, such as congruence).

P :⇔ Q means P is defined to be logically equivalent to Q.

A XOR B :⇔ (A ∨ B) ∧ ¬(A ∧ B)
U+2254 (U+003A U+003D)


U+003A U+229C
≔ (: =)




( )
precedence grouping parentheses; brackets everywhere Perform the operations inside the parentheses first. (8 ÷ 4) ÷ 2 = 2 ÷ 2 = 1, but 8 ÷ (4 ÷ 2) = 8 ÷ 2 = 4. U+0028 U+0029 ( ) (


( )
turnstile proves propositional logic, first-order logic xy means x proves (syntactically entails) y (AB) ⊢ (¬B → ¬A) U+22A2 \vdash
double turnstile models propositional logic, first-order logic xy means x models (semantically entails) y (AB) ⊨ (¬B → ¬A) U+22A8 \vDash, \models

Advanced and rarely used logical symbols

These symbols are sorted by their Unicode value:

  • U+0305  ̅  COMBINING OVERLINE, used as abbreviation for standard numerals (Typographical Number Theory). For example, using HTML style "4̅" is a shorthand for the standard numeral "SSSS0".
    • Overline is also a rarely used format for denoting Gödel numbers: for example, "A ∨ B" says the Gödel number of "(A ∨ B)".
    • Overline is also an outdated[according to whom?] way for denoting negation, still in use in electronics: for example, "A ∨ B" is the same as "¬(A ∨ B)".
  • U+2191 UPWARDS ARROW or U+007C | VERTICAL LINE: Sheffer stroke, the sign for the NAND operator (negation of conjunction).[4]
  • U+2193 DOWNWARDS ARROW Peirce Arrow, the sign for the NOR operator (negation of disjunction).[4]
  • U+2299 CIRCLED DOT OPERATOR the sign for the XNOR operator (negation of exclusive disjunction).
  • U+2204 THERE DOES NOT EXIST: strike out existential quantifier, same as "¬∃"[4]
  • U+2234 THEREFORE: Therefore[4]
  • U+2235 BECAUSE: because[4]
  • U+22A7 MODELS: is a model of (or "is a valuation satisfying")[4]
  • U+22A8 TRUE: is true of
  • U+22AC DOES NOT PROVE: negated ⊢, the sign for "does not prove", for example TP says "P is not a theorem of T"[4]
  • U+22AD NOT TRUE: is not true of
  • U+2020 DAGGER: Affirmation operator (read 'it is true that ...')
  • U+22BC NAND: NAND operator.
  • U+22BD NOR: NOR operator.
  • U+25C7 WHITE DIAMOND: modal operator for "it is possible that", "it is not necessarily not" or rarely "it is not provable not" (in most modal logics it is defined as "¬◻¬")[4]
  • U+22C6 STAR OPERATOR: usually used for ad-hoc operators
  • U+22A5 UP TACK or U+2193 DOWNWARDS ARROW: Webb-operator or Peirce arrow, the sign for NOR. Confusingly, "⊥" is also the sign for contradiction or absurdity.[4]
  • U+231C TOP LEFT CORNER and U+231D TOP RIGHT CORNER: corner quotes, also called "Quine quotes"; for quasi-quotation, i.e. quoting specific context of unspecified ("variable") expressions;[5] also used for denoting Gödel number;[6] for example "⌜G⌝" denotes the Gödel number of G. (Typographical note: although the quotes appears as a "pair" in unicode (231C and 231D), they are not symmetrical in some fonts. And in some fonts (for example Arial) they are only symmetrical in certain sizes. Alternatively the quotes can be rendered as ⌈ and ⌉ (U+2308 and U+2309) or by using a negation symbol and a reversed negation symbol ⌐ ¬ in superscript mode. )
  • U+25FB WHITE MEDIUM SQUARE or U+25A1 WHITE SQUARE: modal operator for "it is necessary that" (in modal logic), or "it is provable that" (in provability logic), or "it is obligatory that" (in deontic logic), or "it is believed that" (in doxastic logic); also as empty clause (alternatives: and ⊥).
  • U+27DB LEFT AND RIGHT TACK: semantic equivalent

The following operators are rarely supported by natively installed fonts.

  • U+27E2 WHITE CONCAVE-SIDED DIAMOND WITH LEFTWARDS TICK: modal operator for was never
  • U+27E3 WHITE CONCAVE-SIDED DIAMOND WITH RIGHTWARDS TICK: modal operator for will never be
  • U+27E4 WHITE SQUARE WITH LEFTWARDS TICK: modal operator for was always
  • U+27E5 WHITE SQUARE WITH RIGHTWARDS TICK: modal operator for will always be
  • U+297D RIGHT FISH TAIL: sometimes used for "relation", also used for denoting various ad hoc relations (for example, for denoting "witnessing" in the context of Rosser's trick) The fish hook is also used as strict implication by C.I.Lewis , the corresponding LaTeX macro is \strictif. See here for an image of glyph. Added to Unicode 3.2.0.

Usage in various countries

Poland and Germany

As of 2014 in Poland, the universal quantifier is sometimes written , and the existential quantifier as .[7][8] The same applies for Germany.[9][10]


The ⇒ symbol is often used in text to mean "result" or "conclusion", as in "We examined whether to sell the product ⇒ We will not sell it". Also, the → symbol is often used to denote "changed to", as in the sentence "The interest rate changed. March 20% → April 21%".

See also


  1. ^ "Named character references". HTML 5.1 Nightly. W3C. Retrieved 9 September 2015.
  2. ^ "Material conditional".
  3. ^ Although this character is available in LaTeX, the MediaWiki TeX system does not support it.
  4. ^ a b c d e f g h i "Comprehensive List of Logic Symbols". Math Vault. 2020-04-06. Retrieved 2020-08-20.
  5. ^ Quine, W.V. (1981): Mathematical Logic, §6
  6. ^ Hintikka, Jaakko (1998), The Principles of Mathematics Revisited, Cambridge University Press, p. 113, ISBN 9780521624985.
  7. ^ "Kwantyfikator ogólny". 2 October 2017 – via Wikipedia.
  8. ^ "Kwantyfikator egzystencjalny". 23 January 2016 – via Wikipedia.
  9. ^ "Quantor". 21 January 2018 – via Wikipedia.
  10. ^ Hermes, Hans. Einführung in die mathematische Logik: klassische Prädikatenlogik. Springer-Verlag, 2013.

Further reading

  • Józef Maria Bocheński (1959), A Précis of Mathematical Logic, trans., Otto Bird, from the French and German editions, Dordrecht, South Holland: D. Reidel.

External links

This page was last edited on 30 March 2021, at 07:38
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