I'm assuming you are asking what is the name of a polygon with eleven sides. That particular polygon has 3 different names:
undecagon, hendecagon, and an 11-gon.
A 5 sided polygon in geometry is a pentagon.
Convex Polygon
The name of a 11 sided polygon is Hendecagon.
geometry
polygon
In geometry, a 17 sided polygon is called a heptadecagon.
It is a dodecagon
Quadrilateral is a polygon with four sides.
Yes it is a term found in math and geometry.
If you mean a hexagon then in geometry it is a 6 sided polygon.
A pentagon is a 5 sided polygon
A 20-sided polygon is called an icosagon. http://www.math.com/tables/geometry/polygons.htm