University of Georgia
University of Georgia: Inter Math: Base (Of a Polygon)
This site provides information about the base(s) of polygons. The site discusses which sides are typically considered bases for triangles and trapezoids. There are links to related terms, more information, and the interactive check point...
Other
Lois Terms: Base of a Polygon
This site gives an explanation of what the base of a polygon is. The base of a polygon when given the location of the altitude is also discussed.