<p><b>Definition: </b>The bottom of a shape, solid or three dimensional object. The base is what the object &#39;rests&#39; on. Base is used in polygons, shapes and solids. The base is used as a reference side for other measurements, most often used in triangles. The base is the surface of the object that is stands on or it is the bottom line.</p><p><b>Examples: </b>The bottom of the triangular based prism is considered the base. The bottom line of the trapezoid can be considered the base.</p>