penta

Penta is a combining form derived from the Greek pente, meaning five. It is used to form terms that denote five units, parts, or features. In English, penta- is often interchangeable with the related prefix pent- depending on historical convention and the word that follows.

In geometry and related fields, penta- appears in names of five-sided or five-faced shapes: pentagon (five-sided polygon), pentagram (five-pointed star), and pentahedron (a polyhedron with five faces). Common examples of pentahedra include the square pyramid and the triangular prism.

In chemistry and biochemistry, penta- indicates five carbon or substituent units: pentane (a five-carbon alkane), pentose (a five-carbon sugar). It also appears in terms describing valence or subunit count, such as pentavalent and pentamer (a molecule or polymer composed of five subunits), and in terms like pentapeptide (five amino acids).

In particle physics, penta- designates five-quark states, as in pentaquarks, a class of hadrons studied at large accelerators. The form also appears in brand names and product designations as a general linguistic element rather than a fixed scientific term.