Prism (geometry)

In <a href="/facts/Geometry/wTQf5ffQ">geometry</a>, a prism is a <a href="/facts/Polyhedron/UC0p9FTF">polyhedron</a> comprising an n-sided polygon <a href="/facts/Base_(geometry)/YkaFWKCF">base</a>, a second base which is a <a href="/facts/Translation_(geometry)/KlpWmnfX">translated</a> copy (rigidly moved without rotation) of the first, and n other <a href="/facts/Face_(geometry)/T2E6BTU4">faces</a>, necessarily all <a href="/facts/Parallelogram/DRuktq60">parallelograms</a>, joining <a href="/facts/Corresponding_sides/UkX6JvjL">corresponding sides</a> of the two bases. All <a href="/facts/Cross_section_(geometry)/g5R1c6v2">cross-sections</a> parallel to the bases are translations of the bases. Prisms are named after their bases, e.g. a prism with a <a href="/facts/Pentagonal/xoq5oJeQ">pentagonal</a> base is called a pentagonal prism. Prisms are a subclass of <a href="/facts/Prismatoid/lPBxnDeG">prismatoids</a>.
Like many basic geometric terms, the word prism (from <a href="/facts/Greek_language/pzDd6eIz">Greek</a> πρίσμα (prisma) 'something sawed') was first used in <a href="/facts/Euclid%2527s_Elements/nPKvCIxs">Euclid's Elements</a>. Euclid defined the term in Book XI as "a solid figure contained by two opposite, equal and parallel planes, while the rest are parallelograms". However, this definition has been criticized for not being specific enough in regard to the nature of the bases (a cause of some confusion amongst generations of later geometry writers).

Prism (geometry) open-in-new

Prism (geometry)