# Orthogonal functions - a coupling of the function

What does $\overline{g(x)}$ mean?

Without any further information, it probably means "apply the function $g$ to the number $x$, and return the complex conjugate of the (complex) number $g$ returns". But there is lots of opportunity for it to be defined as something different in a particular text. –  Henning Makholm Nov 20 '11 at 15:40
Are you dealing with real or complex analysis? In complex analysis, $\overline{g(z)}$ is the complex congugate of $g(z)$. I am not aware of any universal meaning of $\overline{g(z)}$ in real analysis. –  robjohn Nov 20 '11 at 15:41