The prefix quad always means four. A quadrilateral is a polygon
with four sides.
There are many kinds of quadrilateral with
special features which have their own names.
In geometry, a quadrilateral is a polygon with four sides or edges
and four vertices or corners. Sometimes, the term quadrangle is
used, for etymological symmetry with triangle, and sometimes tetragon
for consistency with pentagon (5 sided), hexagon (6 sided) and so
on. The interior angles of a quadrilateral add up to 360 degrees.
