What does pentahedron mean?
A pentahedron is a three-dimensional solid whose surface is made up of five flat faces. Unlike a pentagon, which is a flat shape with five sides, a pentahedron has depth and can take different forms depending on how its faces meet. A square pyramid and a triangular prism are both examples. In geometry, the word is used to classify and describe polyhedral structures, with attention to their vertices, edges, and face arrangements. It is related to the Greek roots for 'five' and 'face' and is also associated with a family of names for solids according to the number of their faces, including the tetrahedron, hexahedron, and octahedron. The word is mainly used in technical, mathematical, architectural, and design contexts, where precise classification is useful.
nounA solid geometric figure with five plane faces and straight edges. In general geometry, the term includes different forms of five-faced polyhedra rather than one single shape.
- A solid polyhedron having five plane faces.
"The transparent model was shaped like a pentahedron, with five clearly visible faces."
"A square pyramid is one example of a pentahedron."
"The geometry lesson focused on identifying vertices, edges, and faces of a pentahedron."
Pentahedra is the standard plural, though pentahedrons is also used in informal or general-audience contexts.
"The two pentahedra were displayed side by side."
A pentahedron can look like a completely different solid depending on how its five faces are arranged, but every one of them is a three-dimensional cousin of the pentagon.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does pentahedron come from?
The word comes from Greek, combining pente, meaning 'five', with -hedron, meaning 'face' or 'plane'. The suffix is widely used in geometry for polyhedra and related forms. English borrowed the word as a term for a solid with five faces, following the established naming pattern of tetrahedron, hexahedron, and octahedron.
Related word forms
How pentahedron is actually used
In general mathematical usage, 'pentahedron' names a category of five-faced polyhedra rather than one uniquely shaped solid. The term is more common in geometry, architecture, and technical description than in everyday speech.
Easily confused with pentahedron
A pentagon is a flat two-dimensional figure with five sides, whereas a pentahedron is a three-dimensional solid with five faces.