Real part

The real part of a complex number $z=x+iy$ is the ordinary real-number component $x$, written $\operatorname{Re}(z)$.

In the complex plane it is the horizontal coordinate. The Riemann Hypothesis says that every non-trivial zero $\rho$ of the zeta function has real part exactly $1/2$.

See also: complex number, imaginary part, critical line, Riemann Hypothesis..