Surd[x,n]
gives the real-valued ![]()
 root of x.
    
   Surd
Surd[x,n]
gives the real-valued ![]()
 root of x.
Details
   - Surd[x,n] returns the real-valued 

 root of real-valued x for odd n.  - Surd[x,n] returns the principal 

 root for non-negative real-valued x and even n. - For symbolic x in Surd[x,n], x is assumed to be real valued.
 - Surd can be evaluated to arbitrary numerical precision.
 - Surd automatically threads over lists. »
 - In StandardForm, Surd[x,n] formats as 
. 
 can be entered as 
surd
, and 
 moves between the fields.- Surd can be used with Interval and CenteredInterval objects. »
 
Examples
open all close allBasic Examples (5)
Scope (31)
Numerical Evaluation (5)
The precision of the output tracks the precision of the input:
Evaluate efficiently at high precision:
Compute the elementwise values of an array using automatic threading:
Or compute the matrix Surd function using MatrixFunction:
Compute worst-case guaranteed intervals using Interval and CenteredInterval objects:
Or compute average-case statistical intervals using Around:
Specific Values (4)
Visualization (4)
Plot the Surd function for various orders:
Visualize the absolute value and argument (sign) of 
 for odd n:
The function 
has the same absolute value but a different argument for 
:
Function Properties (8)
Surd[x,n] is defined for all real x when n is a positive, odd integer:
For positive, even n, it is defined for non-negative x:
For negative n, 0 is removed from the domain:
Surd is not defined for nonreal complex values:
Surd[x,n] achieves all non-negative real values when n is a positive even integer:
For positive odd n, its range is the whole real line:
For negative n, 0 is removed from the range:
Surd[x,n] is not an analytic function of x for any integer n:
Decreasing for negative even 
:
And it is surjective onto 
 for odd, positive 
, but not other values of 
:
It is non-negative on its real domain for even 
:
 in general has both singularities and discontinuities at zero: 
However, for positive odd 
 it is continuous at the origin:
 is neither convex nor concave for odd 
:
On its domain of definition, it is concave for positive even 
 and convex of negative even 
:
Differentiation (3)
Integration (3)
Compute the indefinite integral using Integrate:
Series Expansions (4)
Find the Taylor expansion using Series:
Plots of the first three approximations around 
:
General term in the series expansion using SeriesCoefficient:
Applications (1)
With 
, the real vector field corresponding to the complex function 
 is 
, and the trajectories that follow the field satisfy the differential equation 
. The implicit solution is 
 for real 
, which corresponds to a family of circles that are tangent to the real axis at the origin:
In polar coordinates, the trajectories are 
 for any real 
:
More generally, for 
 where 
 is an integer, the streamlines follow 
 for constant 
:
This also works for negative powers:
For odd powers, care must be taken to ensure the first argument to Surd is non-negative:
Properties & Relations (3)
Possible Issues (1)
Neat Examples (1)
Plot a composition of Surd:
Related Guides
Related Links
History
Text
Wolfram Research (2012), Surd, Wolfram Language function, https://reference.wolfram.com/language/ref/Surd.html.
CMS
Wolfram Language. 2012. "Surd." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/Surd.html.
APA
Wolfram Language. (2012). Surd. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/Surd.html
BibTeX
@misc{reference.wolfram_2025_surd, author="Wolfram Research", title="{Surd}", year="2012", howpublished="\url{https://reference.wolfram.com/language/ref/Surd.html}", note=[Accessed: 04-November-2025]}
BibLaTeX
@online{reference.wolfram_2025_surd, organization={Wolfram Research}, title={Surd}, year={2012}, url={https://reference.wolfram.com/language/ref/Surd.html}, note=[Accessed: 04-November-2025]}