Riemann surface

noun Mathematics.
  1. a geometric representation of a function of a complex variable in which a multiple-valued function is depicted as a single-valued function on several planes, the planes being connected at some of the points at which the function takes on more than one value.

Origin of Riemann surface

First recorded in 1890–95; named after G. F. B. Riemann
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018