List of logic symbols

This article contains logic symbols. Without proper rendering support, you may see question marks, boxes, or other symbols instead of logic symbols.

In logic, a set of symbols is commonly used to express logical representation. The following table lists many common symbols, together with their name, how they should be read out loud, and the related field of mathematics. Additionally, the subsequent columns contains an informal explanation, a short example, the Unicode location, the name for use in HTML documents,^[1] and the LaTeX symbol.

Basic logic symbols

Symbol	Unicode value (hexadecimal)	HTML codes	LaTeX symbol	Logic Name	Read as	Category	Explanation	Examples
⇒ → ⊃	U+21D2 U+2192 U+2283	⇒ → ⊃ ⇒ → ⊃	$\Rightarrow$ \Rightarrow $\implies$ \implies $\to$ \to or \rightarrow $\supset$ \supset	material conditional (material implication)	implies, if P then Q, it is not the case that P and not Q	propositional logic, Boolean algebra, Heyting algebra	$A\Rightarrow B$ is false when $A$ is true and $B$ is false but true otherwise. $\rightarrow$ may mean the same as $\Rightarrow$ (the symbol may also indicate the domain and codomain of a function; see table of mathematical symbols). $\supset$ may mean the same as $\Rightarrow$ (the symbol may also mean superset).	$x=2\Rightarrow x^{2}=4$ is true, but $x^{2}=4\Rightarrow x=2$ is in general false (since $x$ could be −2).
⇔ ↔ ≡	U+21D4 U+2194 U+2261	⇔ ↔ ≡ ⇔ &LeftRightArrow; &equiv;	$\Leftrightarrow$ \Leftrightarrow $\iff$ \iff $\leftrightarrow$ \leftrightarrow $\equiv$ \equiv	material biconditional (material equivalence)	if and only if, iff, xnor	propositional logic, Boolean algebra	$A\Leftrightarrow B$ is true only if both $A$ and $B$ are false, or both $A$ and $B$ are true. Whether a symbol means a material biconditional or a logical equivalence, depends on the author’s style.	$x+5=y+2\Leftrightarrow x+3=y$
¬ ~ !	U+00AC U+007E U+0021	¬ ˜ ! ¬ &tilde; &excl;	$\neg$ \lnot or \neg $\sim$ \sim	negation	not	propositional logic, Boolean algebra	The statement $\lnot A$ is true if and only if $A$ is false. A slash placed through another operator is the same as $\neg$ placed in front.	$\neg (\neg A)\Leftrightarrow A$ $x\neq y\Leftrightarrow \neg (x=y)$
∧ · &	U+2227 U+00B7 U+0026	∧ · & &and; · &	$\wedge$ \wedge or \land $\cdot$ \cdot $\&$ \&^[2]	logical conjunction	and	propositional logic, Boolean algebra	The statement A ∧ B is true if A and B are both true; otherwise, it is false.	$n < 4 \land$ $n >2 \Leftrightarrow$ $n = 3$ when n is a natural number.
∨ + ∥	U+2228 U+002B U+2225	∨ + ∥ &or; + &parallel;	$\lor$ \lor or \vee $\parallel$ \parallel	logical (inclusive) disjunction	or	propositional logic, Boolean algebra	The statement A ∨ B is true if A or B (or both) are true; if both are false, the statement is false.	$n \geq 4 \lor n \leq 2 \Leftrightarrow n \neq 3$ when n is a natural number.
⊕ ⊻ ↮ ≢	U+2295 U+22BB U+21AE U+2262	⊕ ⊻ ↮ ≢ &oplus; &veebar; — &nequiv;	$\oplus$ \oplus $\veebar$ \veebar $\not \equiv$ \not\equiv	exclusive disjunction	xor, either ... or ... (but not both)	propositional logic, Boolean algebra	The statement $A\oplus B$ is true when either A or B, but not both, are true. This is equivalent to ¬(A ↔ B), hence the symbols $\nleftrightarrow$ and $\not \equiv$ .	$\lnot A\oplus A$ is always true and $A\oplus A$ is always false (if vacuous truth is excluded).
⊤ T 1	U+22A4	⊤ &top;	$\top$ \top	true (tautology)	top, truth, tautology, verum, full clause	propositional logic, Boolean algebra, first-order logic	$\top$ denotes a proposition that is always true.	The proposition $\top \lor P$ is always true since at least one of the two is unconditionally true.
⊥ F 0	U+22A5	⊥ &perp;	$\bot$ \bot	false (contradiction)	bottom, falsity, contradiction, falsum, empty clause	propositional logic, Boolean algebra, first-order logic	$\bot$ denotes a proposition that is always false. The symbol ⊥ may also refer to perpendicular lines.	The proposition $\bot \wedge P$ is always false since at least one of the two is unconditionally false.
∀ ()	U+2200	∀ ∀	$\forall$ \forall	universal quantification	given any, for all, for every, for each, for any	first-order logic	$\forall x$ $P(x)$ or $(x)$ $P(x)$ says “given any $x$ , $x$ has property $P$ .”	$\forall n\in \mathbb {N} :n^{2}\geq n.$
∃	U+2203	∃ ∃	$\exists$ \exists	existential quantification	there exists, for some	first-order logic	$\exists x$ $P(x)$ says “there exists an $x$ (at least one) such that $x$ has property $P$ .”	$\exists n\in \mathbb {N} :$ n is even.
∃!	U+2203 U+0021	∃ ! ∃!	$\exists !$ \exists !	uniqueness quantification	there exists exactly one	first-order logic (abbreviation)	$\exists !x$ $P(x)$ says “there exists exactly one $x$ such that $x$ has property $P$ .” Only $\forall$ and $\exists$ are part of formal logic. $\exists !x$ $P(x)$ is an abbreviation for $\exists x\forall y(P(y)\leftrightarrow y=x)$	$\exists !n\in \mathbb {N} :n+5=2n.$
( )	U+0028 U+0029	( ) ( )	$(~)$ ( )	precedence grouping	parentheses; brackets	almost all logic syntaxes, as well as metalanguage	Perform the operations inside the parentheses first.	$(8 \div 4) \div 2 = 2 \div 2 = 1$ , but $8 \div (4 \div 2) = 8 \div 2 = 4$ .
$\mathbb {D}$	U+1D53B	𝔻 &Dopf;	\mathbb{D}	domain of discourse	domain of discourse	metalanguage (first-order logic semantics)		$\mathbb {D} \mathbb {:} \mathbb {R}$
⊢	U+22A2	⊢ &vdash;	$\vdash$ \vdash	turnstile	syntactically entails (proves)	metalanguage (metalogic)	$A\vdash B$ says “ $B$ is a theorem of $A$ ”. In other words, $A$ proves $B$ via a deductive system.	$(A\rightarrow B)\vdash (\lnot B\rightarrow \lnot A)$ (eg. by using natural deduction)
⊨	U+22A8	⊨ &vDash;	$\vDash$ \vDash, \models	double turnstile	semantically entails	metalanguage (metalogic)	$A\vDash B$ says “in every model, it is not the case that $A$ is true and $B$ is false”.	$(A\rightarrow B)\vDash (\lnot B\rightarrow \lnot A)$ (eg. by using truth tables)
≡ ⟚ ⇔	U+2261 U+27DA U+21D4	≡ — ⇔ &equiv; — ⇔	$\equiv$ \equiv $\Leftrightarrow$ \Leftrightarrow	logical equivalence	is logically equivalent to	metalanguage (metalogic)	It’s when $A\vDash B$ and $B\vDash A$ . Whether a symbol means a material biconditional or a logical equivalence, depends on the author’s style.	$(A\rightarrow B)\equiv (\lnot A\lor B)$
⊬	U+22AC		⊬\nvdash		does not syntactically entail (does not prove)	metalanguage (metalogic)	$A\nvdash B$ says “ $B$ is not a theorem of $A$ ”. In other words, $B$ is not derivable from $A$ via a deductive system.	$A\lor B\nvdash A\wedge B$
⊭	U+22AD		⊭\nvDash		does not semantically entail	metalanguage (metalogic)	$A\nvDash B$ says “ $A$ does not guarantee the truth of $B$ ”. In other words, $A$ does not make $B$ true.	$A\lor B\nvDash A\wedge B$
□	U+25A1		$\Box$ \Box	necessity (in a model)	box; it is necessary that	modal logic	modal operator for “it is necessary that” in alethic logic, “it is provable that” in provability logic, “it is obligatory that” in deontic logic, “it is believed that” in doxastic logic.	$\Box \forall xP(x)$ says “it is necessary that everything has property $P$ ”
◇	U+25C7		$\Diamond$ \Diamond	possibility (in a model)	diamond; it is possible that	modal logic	modal operator for “it is possible that”, (in most modal logics it is defined as “¬□¬”, “it is not necessarily not”).	$\Diamond \exists xP(x)$ says “it is possible that something has property $P$ ”
∴	U+2234		∴\therefore	therefore	therefore	metalanguage	abbreviation for “therefore”.
∵	U+2235		∵\because	because	because	metalanguage	abbreviation for “because”.
≔ ≜ ≝	U+2254 U+225C U+225D	≔ &coloneq;	$:=$ := $\triangleq$ \triangleq ${\stackrel {\scriptscriptstyle \mathrm {def} }{=}}$ \stackrel{ \scriptscriptstyle \mathrm{def}}{=}	definition	is defined as	metalanguage	$a:=b$ means "from now on, $a$ is defined to be another name for $b$ ." This is a statement in the metalanguage, not the object language. The notation $a\equiv b$ may occasionally be seen in physics, meaning the same as $a:=b$ .	$\cosh x:={\frac {e^{x}+e^{-x}}{2}}$

Advanced or rarely used logical symbols

The following symbols are either advanced and context-sensitive or very rarely used:

Symbol	Unicode value (hexadecimal)	LaTeX symbol	Logic Name	Read as	Category	Explanation
⥽	U+297D	\strictif	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 $p$ ⥽ $q\equiv \Box (p\rightarrow q)$ .
̅	U+0305		combining overline			Used format for denoting Gödel numbers. Using HTML style “4̅” is an abbreviation for the standard numeral “SSSS0”. It may also denote a negation (used primarily in electronics).
⌜ ⌝	U+231C U+231D	\ulcorner \urcorner	top left corner top right corner			Corner quotes, also called “Quine quotes”; for quasi-quotation, i.e. quoting specific context of unspecified (“variable”) expressions;^[3] also used for denoting Gödel number;^[4] 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. 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+2204	\nexists	there does not exist			Strike out existential quantifier. “¬∃” is recommended instead. ^{[by whom?]}
↑ \|	U+2191 U+007C		upwards arrow vertical line			Sheffer stroke, the sign for the NAND operator (negation of conjunction).
↓	U+2193		downwards arrow			Peirce Arrow, a sign for the NOR operator (negation of disjunction).
⊼	U+22BC		NAND			A new symbol made specifically for the NAND operator.
⊽	U+22BD		NOR			A new symbol made specifically for the NOR operator.
⊙	U+2299	\odot	circled dot operator			A sign for the XNOR operator (material biconditional and XNOR are the same operation).
⟛	U+27DB		left and right tack			“Proves and is proved by”.
⊧	U+22A7		models			“Is a model of” or “is a valuation satisfying”.
⊩	U+22A9		forces			One of this symbol’s uses is to mean “truthmakes” in the truthmaker theory of truth. It is also used to mean “forces” in the set theory method of forcing.
⟡	U+27E1		white concave-sided diamond	never	modal operator
⟢	U+27E2		white concave-sided diamond with leftwards tick	was never	modal operator
⟣	U+27E3		white concave-sided diamond with rightwards tick	will never be	modal operator
⟤	U+25A4		white square with leftwards tick	was always	modal operator
⟥	U+25A5		white square with rightwards tick	will always be	modal operator
⋆	U+22C6		star operator			May sometimes be used for ad-hoc operators.
⌐	U+2310		reversed not sign
⨇	U+2A07		two logical AND operator

References

^ "Named character references". HTML 5.1 Nightly. W3C. Retrieved 9 September 2015.
^ Although this character is available in LaTeX, the MediaWiki TeX system does not support it.
^ Quine, W.V. (1981): Mathematical Logic, §6
^ Hintikka, Jaakko (1998), The Principles of Mathematics Revisited, Cambridge University Press, p. 113, ISBN 9780521624985.

External links

Named character entities in HTML 4.0

[1] "Named character references". HTML 5.1 Nightly. W3C. Retrieved 9 September 2015.

[2] Although this character is available in LaTeX, the MediaWiki TeX system does not support it.

[3] Quine, W.V. (1981): Mathematical Logic, §6

[4] Hintikka, Jaakko (1998), The Principles of Mathematics Revisited, Cambridge University Press, p. 113, ISBN 9780521624985.

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List of logic symbols

Contents

Basic logic symbols

Advanced or rarely used logical symbols

See also

References

Further reading

External links