  Ionic-pair equal-time displacement correlations in relaxor lead magnesium
niobate, $Pb(Mg_{1/3}Nb_{2/3})O_{3}$, have been investigated at room
temperature in terms of an x-ray diffuse scattering technique. Functions of the
distinct correlations have been determined quantitatively. The results show the
significantly strong rhombohedral-polar correlations regarding Pb-O, Mg/Nb-O,
and O-O' pairs. Their spatial distribution forms an ellipse or a sphere with
the radii of 30-80$\AA$. This observation of local structure in the system
proves precursory presence of the polar microregions in the paraelectric state
which leads to the dielectric dispersion.
