<para>Computes the geometric center of a geometry, or equivalently,
the center of mass of the geometry as a <varname>POINT</varname>. For
[<varname>MULTI</varname>]<varname>POINT</varname>s, this is computed
- as the arithmetric mean of the input coordinates. For
+ as the arithmetic mean of the input coordinates. For
[<varname>MULTI</varname>]<varname>LINESTRING</varname>s, this is
computed as the weighted length of each line segment. For
[<varname>MULTI</varname>]<varname>POLYGON</varname>s, "weight" is