A branch point whose neighborhood of values wrap around an infinite number of times as their complex
arguments are varied. The point 
under the function 
is therefore a logarithmic branch point. Logarithmic branch
points are equivalent to logarithmic singularities.
Logarithmic Branch Point
See also
Algebraic Branch Point, Branch Point, Logarithmic SingularityExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Logarithmic Branch Point." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/LogarithmicBranchPoint.html