The wave function of a system of two particles (such as electrons) in three-dimensional space is a function that depends on the positions of both particles. Each particle’s position is described by three coordinates, so the wave function depends on six real variables in total. The wave function maps these six real variables to a complex number, representing the probability amplitude.

Thus, the wave function is a function from R6 (the six-dimensional space of the two particles’ positions) to
C2 (the complex numbers).