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Frustum
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<p>In <a href="/facts/Geometry/wTQf5ffQ">geometry</a>, a frustum ; (pl.: frusta or frustums) is the portion of a <a href="/facts/Polyhedron/UC0p9FTF">solid</a> (normally a <a href="/facts/Pyramid_(geometry)/fCXRgFwu">pyramid</a> or a <a href="/facts/Cone_(geometry)/2c9GIzYD">cone</a>) that lies between two <a href="/facts/Parallel_planes/16r5yq7D">parallel planes</a> cutting the solid. In the case of a pyramid, the base faces are <a href="/facts/Polygonal/yAq7RjPz">polygonal</a> and the side faces are <a href="/facts/Trapezoidal/nCBKsauz">trapezoidal</a>. A <i>right frustum</i> is a <a href="/facts/Right_pyramid/fCXRgFwu">right pyramid</a> or a right cone <a href="/facts/Truncation_(geometry)/DYb589Je">truncated</a> perpendicularly to its axis; otherwise, it is an <i>oblique frustum</i>. In a <i><a href="/facts/Truncated_cone/TEfLWynX">truncated cone</a></i> or <i><a href="/facts/Truncated_pyramid/TEfLWynX">truncated pyramid</a></i>, the truncation plane is not necessarily parallel to the cone's base, as in a frustum. If all its edges are forced to become of the same length, then a frustum becomes a <i><a href="/facts/Prism_(geometry)/baIRRkCy">prism</a></i> (possibly oblique or/and with irregular bases). </p>