Conjugate[z]
or z gives the complex conjugate of the complex number z.
Conjugate
Conjugate[z]
or z gives the complex conjugate of the complex number z.
Details
- Mathematical function, suitable for both symbolic and numerical manipulation.
- can be entered as
co
,
conj
, or \[Conjugate]. - Conjugate automatically threads over lists. »
- Conjugate can be used with Interval and CenteredInterval objects. »
Examples
open all close allBasic Examples (4)
Conjugate[1 + I]Use
conj
to conjugate expressions:
(1 + I)Plot over a subset of the reals:
Plot[Conjugate[x], {x, -3, 3}]Plot over a subset of the complexes:
ComplexPlot3D[Conjugate[z], {z, -2 - 2I, 2 + 2I}, PlotLegends -> Automatic]Scope (24)
Numerical Evaluation (6)
Conjugate[.7]Conjugate[.5 + I]N[Conjugate[2 / 3 + I], 25]The precision of the output tracks the precision of the input:
Conjugate[2.3000000000000000000000000 - 1 / I]Evaluate efficiently at high precision:
Conjugate[I + 1 / 3`100]//TimingConjugate[5 I + 11 / 7`10000];//TimingCompute the elementwise values of an array using automatic threading:
Conjugate[{{1 / 2, -1 - I}, {-5 / 3, 1 / 2 + I}}]Or compute the matrix Conjugate function using MatrixFunction:
MatrixFunction[Conjugate, {{1 / 2, -1 - I}, {-5 / 3, 1 / 2 + I}}]//FullSimplifyConjugate can be used with Interval and CenteredInterval objects:
Conjugate[Interval[{-5, 5}]]Conjugate[CenteredInterval[-5 - 3I, 1 + I]]Or compute average-case statistical intervals using Around:
Conjugate[ Around[-1.1 + I, 0.01]]Specific Values (3)
Values of Conjugate at fixed points:
Table[Conjugate[n ], {n, {2I , -1 / 3, 3 + 4I}}]Conjugate[0]Conjugate[I Infinity]Conjugate[ComplexInfinity]Visualization (4)
Plot the real and imaginary parts of
and
over the reals:
ReImPlot[{x + I, Conjugate[x + I]}, {x, -3, 3}, PlotLegends -> Automatic]Plot the absolute value of
function:
Plot[Abs[Conjugate[x + I]], {x, -3, 3}]Compare the plots of
and
in three dimensions:
GraphicsRow[ComplexPlot3D[#, {z, -2 - 2I, 2 + 2I}, Mesh -> Automatic, RegionFunction -> Function[{z}, Abs[z] ≤ 2]]& /@ {z, Conjugate[z]}, ImageSize -> Medium]Plot the real part of
function:
ComplexContourPlot[Re[Conjugate[z ^ 2]], {z, -3 - 3 I, 3 + 3I}, Contours -> 20]Plot the imaginary part of
function:
ComplexContourPlot[Im[Conjugate[z ^ 2]], {z, -3 - 3 I, 3 + 3I}, Contours -> 20]Function Properties (11)
Conjugate is defined for all real and complex inputs:
FunctionDomain[Conjugate[x], x]FunctionDomain[Conjugate[x], x, Complexes]The range of Conjugate is all real and complex values:
FunctionRange[Conjugate[x], x, y]FunctionRange[Conjugate[x], x, y, Complexes]Conjugate is an odd function:
Conjugate[-z]Conjugate is involutive,
:
Conjugate[Conjugate[z]]Conjugate is not a differentiable function:
D[Conjugate[x], x]The difference quotient does not have a limit in the complex plane:
Underscript[, hUnderscript[ -> , ℂ]0](Conjugate[x + h] - Conjugate[x]/h)The limit has different values in different directions, for example,
in the real direction:
Underscript[, hUnderscript[ -> , ℝ]0](Conjugate[1 + h] - Conjugate[1]/h)But in the imaginary direction, the limit is
:
Limit[(Conjugate[1 + h] - Conjugate[1]/h), h -> 0, Direction -> -I]Conjugate is not an analytic function:
FunctionAnalytic[Conjugate[x], x, Complexes]It is singular everywhere but continuous:
FunctionSingularities[Conjugate[x], x, Complexes]FunctionDiscontinuities[Conjugate[x], x, Complexes]Conjugate is nondecreasing on the real line:
FunctionMonotonicity[Conjugate[x], x]Conjugate is injective on the real line:
FunctionInjective[Conjugate[x], x]Plot[{Conjugate[x], 1}, {x, -4, 4}]Conjugate is surjective on the real line:
FunctionSurjective[Conjugate[x], x]Plot[{Conjugate[x], -2.5}, {x, -4, 4}]Conjugate is neither non-negative nor non-positive:
FunctionSign[Conjugate[x], x]TraditionalForm formatting:
Conjugate[z]//TraditionalFormApplications (6)
Define a scalar product for complex‐valued lists utilizing BraKet notation:
BraKet[{a_}, {b_}] := Conjugate[a].bBraKet[{{1, I}}, {{1I, 2}}]Rewrite a complex-valued rational function into one with real denominator:
toRealDenominator[rat_] := With[{c = ComplexExpand[Conjugate[Denominator[rat]]]}, Expand[Numerator[rat] c] / Expand[Denominator[rat] c]]toRealDenominator[1 / (x ^ 2 + 3 I x - 2 + 4I)]Recover the original fraction:
Cancel[%]Implement a Möbius transformation:
MöbiusTransformation[a_, z_] := (z - a) / (1 - Conjugate[a] z)Plot the images of concentric circles:
a = 1 + 2I;
ParametricPlot[Evaluate[Table[{Re[MöbiusTransformation[a, ρ Exp[I ϕ]]], Im[MöbiusTransformation[a, ρ Exp[I ϕ]]]}, {ρ, 0, 1, 1 / 10}]], {ϕ, 0, 2Pi}]Write a real‐valued function as a function of z and z:
toCCForm[f_, {x_, y_}, z_] := f /. {x -> (z + Conjugate[z]) / 2, y -> (z - Conjugate[z]) / (2I)}toCCForm[x^3 - 3 x y^2, {x, y}, z] //SimplifyHolomorphic functions are independent of z:
toCCForm[x^3 - 3 x y^2 + I (3 x^2 y - y^3), {x, y}, z]//SimplifyUse Conjugate to describe geometric regions:
Block[{z = x + I y}, RegionPlot[Abs[Conjugate[z] Re[z] + z Im[z]] < 1, {x, -2, 2}, {y, -2, 2}]]In quantum mechanics, systems with finitely many states are represented by unit vectors and physical quantities by matrices that act on them. Consider a spin-1/2 particle such as an electron in the following state:
s = {(1/Sqrt[5]), (2I/Sqrt[5])};The operator for the
component of angular momentum is given by the following matrix:
jz = (ℏ/2)PauliMatrix[3]Compute the expected angular momentum in this state as
:
Conjugate[s].jz.sThe uncertainty in the angular momentum is
:
σz = Simplify[Sqrt[Conjugate[s].jz.jz.s - (Conjugate[s].jz.s)^2], ℏ > 0]The uncertainty in the
component of angular momentum is computed analogously:
jy = (ℏ/2)PauliMatrix[2]σy = Simplify[Sqrt[Conjugate[s].jy.jy.s - (Conjugate[s].jy.s)^2], ℏ > 0]The uncertainty principle gives a lower bound on the product of uncertainties,
:
Simplify[σy σz > (ℏ/2)Abs[ Conjugate[s].(jy.jz - jz.jy).s] , ℏ > 0]Properties & Relations (7)
Some transformations are performed automatically:
Conjugate[1 / z]Conjugate[Re[z]]Conjugate is its own inverse:
Conjugate[Conjugate[z]]Simplify expressions containing Conjugate:
z Conjugate[z]FullSimplify[%]Conjugate[z1 z2] - Conjugate[z1]Conjugate[z2]FullSimplify[%]Conjugate[x + I y]ComplexExpand[%]Assume generic complex‐valued variables:
ComplexExpand[Conjugate[z], z]ComplexExpand[Conjugate[Sqrt[z]], z]Use Conjugate as an option value in ComplexExpand:
ComplexExpand[Re[x], x, TargetFunctions -> {Conjugate}]Integrate along a line in the complex plane, symbolically and numerically:
Integrate[Conjugate[x ^ 2], {x, -2 + I, Pi + 2I}]N[%]NIntegrate[Conjugate[x ^ 2], {x, -2 + I, Pi + 2I}]Find Hermitian conjugate of a matrix:
m = RandomComplex[{-1 - I, 1 + I}, {2, 2}];Conjugate[Transpose[m]]//MatrixFormUse ConjugateTranspose instead:
ConjugateTranspose[m]//MatrixFormPossible Issues (4)
Conjugate does not always propagate into arguments:
Conjugate[Sin[z]]Conjugate[Exp[z]]Differentiating Conjugate is not possible:
D[Conjugate[t], t]The limit that defines the derivative is direction dependent and therefore does not exist:
Limit[DifferenceQuotient[Conjugate[z], {z, h}], h -> 0, Direction -> 1]Limit[DifferenceQuotient[Conjugate[z], {z, h}], h -> 0, Direction -> I]Use ComplexExpand to get differentiable expressions for real-valued variables:
D[ComplexExpand[Conjugate[x + I y]], y]Conjugate can stay unevaluated for numeric arguments:
Conjugate[ArcSin[(-1 - 2 E - E ^ 2 + (1 + E) ^ 2)]]Simplify[%]Machine‐precision numeric evaluation of Conjugate can give wrong results:
Conjugate[ArcSin[(-1 - 2 E - E ^ 2 + (1 + E) ^ 2) + 10 ^ -20]]N[%]Use arbitrary precision evaluation instead:
N[%%, 20]See Also
ConjugateTranspose ComplexExpand Transpose Arg Im Complex BraKet
Characters: \[Conjugate]
Function Repository: ComplexD
Tech Notes
Related Links
History
Introduced in 1988 (1.0) | Updated in 2003 (5.0) ▪ 2004 (5.1) ▪ 2021 (13.0)
Text
Wolfram Research (1988), Conjugate, Wolfram Language function, https://reference.wolfram.com/language/ref/Conjugate.html (updated 2021).
CMS
Wolfram Language. 1988. "Conjugate." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2021. https://reference.wolfram.com/language/ref/Conjugate.html.
APA
Wolfram Language. (1988). Conjugate. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Conjugate.html
BibTeX
@misc{reference.wolfram_2026_conjugate, author="Wolfram Research", title="{Conjugate}", year="2021", howpublished="\url{https://reference.wolfram.com/language/ref/Conjugate.html}", note=[Accessed: 12-June-2026]}
BibLaTeX
@online{reference.wolfram_2026_conjugate, organization={Wolfram Research}, title={Conjugate}, year={2021}, url={https://reference.wolfram.com/language/ref/Conjugate.html}, note=[Accessed: 12-June-2026]}