x1 is a pure real number (such that its imaginary part is 0) understood as an example of a complex number.
Includes 0 = (0,0) = 0 + 0i. This word relies on xo'ei implicitly filling the second slot of "ka'o" and also relies on the Cartesian decomposition of all complex numbers into real and imaginary bases (due to ka'o). It is important to note that this is isomorphic to a 'normal' real number but is not one; it is a complex number with imaginary part 0. See also: ka'o zei namcu and nozeika'o zei namcu.