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In geometry, a **Johnson solid**, sometimes also known as a **Johnson–Zalgaller solid**, is a strictly convex polyhedron whose faces are regular polygons. They are sometimes defined to exclude the uniform polyhedrons. There are ninety-two solids with such a property: the first solids are the pyramids, cupolas. and a rotunda; some of the solids may be constructed by attaching with those previous solids, whereas others may not. These solids are named after mathematicians Norman Johnson and Victor Zalgaller.

A Johnson solid is a convex polyhedron whose faces are all regular polygons.^{[1]} Here, a polyhedron is said to be convex if the shortest path between any two of its vertices lies either within its interior or on its boundary, none of its faces are coplanar (meaning they do not share the same plane, and do not "lie flat"), and none of its edges are colinear (meaning they are not segments of the same line).^{[2]}^{[3]} Although there is no restriction that any given regular polygon cannot be a face of a Johnson solid, some authors required that Johnson solids are not uniform. This means that a Johnson solid is not a Platonic solid, Archimedean solid, prism, or antiprism.^{[4]}^{[5]} A convex polyhedron in which all faces are nearly regular, but some are not precisely regular, is known as a near-miss Johnson solid.^{[6]}

The Johnson solid, sometimes known as Johnson–Zalgaller solid, was named after two mathematicians Norman Johnson and Victor Zalgaller.^{[7]} Johnson (1966) published a list including ninety-two Johnson solids—excluding the five Platonic solids, the thirteen Archimedean solids, the infinitely many uniform prisms, and the infinitely many uniform antiprisms—and gave them their names and numbers. He did not prove that there were only ninety-two, but he did conjecture that there were no others.^{[8]} Zalgaller (1969) proved that Johnson's list was complete.^{[9]}

The naming of Johnson solids follows a flexible and precise descriptive formula that allows many solids to be named in multiple different ways without compromising the accuracy of each name as a description. Most Johnson solids can be constructed from the first few solids (pyramids, cupolae, and a rotunda), together with the Platonic and Archimedean solids, prisms, and antiprisms; the center of a particular solid's name will reflect these ingredients. From there, a series of prefixes are attached to the word to indicate additions, rotations, and transformations:^{[10]}

*Bi-*indicates that two copies of the solid are joined base-to-base. For cupolae and rotundas, the solids can be joined so that either like faces (*ortho-*) or unlike faces (*gyro-*) meet. Using this nomenclature, a pentagonal bipyramid is a solid constructed by attaching two bases of pentagonal pyramids. Triangular orthobicupola is constructed by two triangular cupolas along their bases.*Elongated*indicates a prism is joined to the base of the solid, or between the bases;*gyroelongated*indicates an antiprism.*Augmented*indicates another polyhedron, namely a pyramid or cupola, is joined to one or more faces of the solid in question.*Diminished*indicates a pyramid or cupola is removed from one or more faces of the solid in question.*Gyrate*indicates a cupola mounted on or featured in the solid in question is rotated such that different edges match up, as in the difference between ortho- and gyrobicupolae.

The last three operations—*augmentation*, *diminution*, and *gyration*—can be performed multiple times for certain large solids. *Bi-* & *Tri-* indicate a double and triple operation respectively. For example, a *bigyrate* solid has two rotated cupolae, and a *tridiminished* solid has three removed pyramids or cupolae. In certain large solids, a distinction is made between solids where altered faces are parallel and solids where altered faces are oblique. *Para-* indicates the former, that the solid in question has altered parallel faces, and *meta-* the latter, altered oblique faces. For example, a *parabiaugmented* solid has had two parallel faces augmented, and a *metabigyrate* solid has had two oblique faces gyrated.^{[10]}

The last few Johnson solids have names based on certain polygon complexes from which they are assembled. These names are defined by Johnson with the following nomenclature:^{[10]}

- A
*lune*is a complex of two triangles attached to opposite sides of a square. *Spheno*- indicates a wedgelike complex formed by two adjacent lunes.*Dispheno-*indicates two such complexes.*Hebespheno*- indicates a blunt complex of two lunes separated by a third lune.*Corona*is a crownlike complex of eight triangles.*Megacorona*is a larger crownlike complex of twelve triangles.- The suffix -
*cingulum*indicates a belt of twelve triangles.

The enumeration of Johnson solids may be denoted as , where denoted the list's enumeration (an example is denoted the first Johnson solid, the equilateral square pyramid).^{[7]} The following is the list of ninety-two Johnson solids, with the enumeration followed according to the list of Johnson (1966):

- Equilateral square pyramid
- Pentagonal pyramid
- Triangular cupola
- Square cupola
- Pentagonal cupola
- Pentagonal rotunda
- Elongated triangular pyramid
- Elongated square pyramid
- Elongated pentagonal pyramid
- Gyroelongated square pyramid
- Gyroelongated pentagonal pyramid
- Triangular bipyramid
- Pentagonal bipyramid
- Elongated triangular bipyramid
- Elongated square bipyramid
- Elongated pentagonal bipyramid
- Gyroelongated square bipyramid
- Elongated triangular cupola
- Elongated square cupola
- Elongated pentagonal cupola
- Elongated pentagonal rotunda
- Gyroelongated triangular cupola
- Gyroelongated square cupola
- Gyroelongated pentagonal cupola
- Gyroelongated pentagonal rotunda
- Gyrobifastigium
- Triangular orthobicupola
- Square orthobicupola
- Square gyrobicupola
- Pentagonal orthobicupola
- Pentagonal gyrobicupola
- Pentagonal orthocupolarotunda
- Pentagonal gyrocupolarotunda
- Pentagonal orthobirotunda
- Elongated triangular orthobicupola
- Elongated triangular gyrobicupola
- Elongated square gyrobicupola
- Elongated pentagonal orthobicupola
- Elongated pentagonal gyrobicupola
- Elongated pentagonal orthocupolarotunda
- Elongated pentagonal gyrocupolarotunda
- Elongated pentagonal orthobirotunda
- Elongated pentagonal gyrobirotunda
- Gyroelongated triangular bicupola
- Gyroelongated square bicupola
- Gyroelongated pentagonal bicupola
- Gyroelongated pentagonal cupolarotunda
- Gyroelongated pentagonal birotunda
- Augmented triangular prism
- Biaugmented triangular prism
- Triaugmented triangular prism
- Augmented pentagonal prism
- Biaugmented pentagonal prism
- Augmented hexagonal prism
- Parabiaugmented hexagonal prism
- Metabiaugmented hexagonal prism
- Triaugmented hexagonal prism
- Augmented dodecahedron
- Parabiaugmented dodecahedron
- Metabiaugmented dodecahedron
- Triaugmented dodecahedron
- Metabidiminished icosahedron
- Tridiminished icosahedron
- Augmented tridiminished icosahedron
- Augmented truncated tetrahedron
- Augmented truncated cube
- Biaugmented truncated cube
- Augmented truncated dodecahedron
- Parabiaugmented truncated dodecahedron
- Metabiaugmented truncated dodecahedron
- Triaugmented truncated dodecahedron
- Gyrate rhombicosidodecahedron
- Parabigyrate rhombicosidodecahedron
- Metabigyrate rhombicosidodecahedron
- Trigyrate rhombicosidodecahedron
- Diminished rhombicosidodecahedron
- Paragyrate diminished rhombicosidodecahedron
- Metagyrate diminished rhombicosidodecahedron
- Bigyrate diminished rhombicosidodecahedron
- Parabidiminished rhombicosidodecahedron
- Metabidiminished rhombicosidodecahedron
- Gyrate bidiminished rhombicosidodecahedron
- Tridiminished rhombicosidodecahedron
- Snub disphenoid
- Snub square antiprism
- Sphenocorona
- Augmented sphenocorona
- Sphenomegacorona
- Hebesphenomegacorona
- Disphenocingulum
- Bilunabirotunda
- Triangular hebesphenorotunda

Some of the Johnson solids may be categorized as *elementary polyhedra*. This means the polyhedron cannot be separated by a plane to create two small convex polyhedrons with regular faces; examples of Johnson solids are the first six Johnson solids—square pyramid, pentagonal pyramid, triangular cupola, square cupola, pentagonal cupola, and pentagonal rotunda—tridiminished icosahedron, parabidiminished rhombicosidodecahedron, tridiminished rhombicosidodecahedron, snub disphenoid, snub square antiprism, sphenocorona, sphenomegacorona, hebesphenomegacorona, disphenocingulum, bilunabirotunda, and triangular hebesphenorotunda.^{[8]}^{[11]}

As the definition above, a Johnson solid is a convex polyhedron with regular polygons as their faces. However, there are several properties possessed by each of them.

- They have Rupert property, meaning they do have polyhedrons of the same or larger size that may pass through a hole inside of them. However, the other five Johnson solids do not have this property: gyrate rhombicosidodecahedron, parabigyrate rhombicosidodecahedron, metabigyrate rhombicosidodecahedron, trigyrate rhombicosidodecahedron, and paragyrate diminished rhombicosidodecahedron.
^{[12]} - From all of the Johnson solids, the elongated square gyrobicupola (also called the pseudorhombicuboctahedron) is unique in being locally vertex-uniform: there are four faces at each vertex, and their arrangement is always the same: three squares and one triangle. However, it is not vertex-transitive, as it has different isometry at different vertices, making it a Johnson solid rather than an Archimedean solid.
^{[13]}^{[14]}^{[15]}

**^**Diudea, M. V. (2018).*Multi-shell Polyhedral Clusters*. Springer. p. 39. doi:10.1007/978-3-319-64123-2. ISBN 978-3-319-64123-2.**^**Litchenberg, Dorovan R. (1988). "Pyramids, Prisms, Antiprisms, and Deltahedra".*The Mathematics Teacher*.**81**(4): 261–265. JSTOR 27965792.**^**Boissonnat, J. D.; Yvinec, M. (June 1989).*Probing a scene of non convex polyhedra*.*Proceedings of the fifth annual symposium on Computational geometry*. pp. 237–246. doi:10.1145/73833.73860.**^**Todesco, Gian Marco (2020). "Hyperbolic Honeycomb". In Emmer, Michele; Abate, Marco (eds.).*Imagine Math 7: Between Culture and Mathematics*. Springer. p. 282. doi:10.1007/978-3-030-42653-8. ISBN 978-3-030-42653-8.**^**Williams, Kim; Monteleone, Cosino (2021).*Daniele Barbaro’s Perspective of 1568*. Springer. p. 23. doi:10.1007/978-3-030-76687-0. ISBN 978-3-030-76687-0.**^**Kaplan, Craig S.; Hart, George W. (2001). "Symmetrohedra: Polyhedra from Symmetric Placement of Regular Polygons" (PDF).*Bridges: Mathematical Connections in Art, Music and Science*: 21–28.- ^
^{a}^{b}Uehara, Ryuhei (2020).*Introduction to Computational Origami: The World of New Computational Geometry*. Springer. p. 62. doi:10.1007/978-981-15-4470-5. ISBN 978-981-15-4470-5. - ^
^{a}^{b}Johnson, Norman (1966). "Convex Solids with Regular Faces".*Canadian Journal of Mathematics*.**18**: 169–200. doi:10.4153/CJM-1966-021-8. **^**Zalgaller, Victor A. (1969).*Convex Polyhedra with Regular Faces*. Consultants Bureau.- ^
^{a}^{b}^{c}Berman, Martin (1971). "Regular-faced convex polyhedra".*Journal of the Franklin Institute*.**291**(5): 329–352. doi:10.1016/0016-0032(71)90071-8. MR 0290245. **^**Hartshorne, Robin (2000).*Geometry: Euclid and Beyond*. Undergraduate Texts in Mathematics. Springer-Verlag. p. 464. ISBN 9780387986500.**^**Fredriksson, Albin (2024). "Optimizing for the Rupert property".*The American Mathematical Monthly*.**131**(3): 255–261. arXiv:2210.00601. doi:10.1080/00029890.2023.2285200.**^**Cromwell, Peter R. (1997).*Polyhedra*. Cambridge University Press. p. 91. ISBN 978-0-521-55432-9.**^**Grünbaum, Branko (2009). "An enduring error" (PDF).*Elemente der Mathematik*.**64**(3): 89–101. doi:10.4171/EM/120. MR 2520469. Reprinted in Pitici, Mircea, ed. (2011).*The Best Writing on Mathematics 2010*. Princeton University Press. pp. 18–31.**^**Lando, Sergei K.; Zvonkin, Alexander K. (2004).*Graphs on Surfaces and Their Applications*. Springer. p. 114. doi:10.1007/978-3-540-38361-1. ISBN 978-3-540-38361-1.

- Gagnon, Sylvain (1982). "Les polyèdres convexes aux faces régulières" [Convex polyhedra with regular faces] (PDF).
*Structural Topology*(6): 83–95. - Paper Models of Polyhedra Archived 2013-02-26 at the Wayback Machine Many links
- Johnson Solids by George W. Hart.
- Images of all 92 solids, categorized, on one page
- Weisstein, Eric W. "Johnson Solid".
*MathWorld*. - VRML models of Johnson Solids by Jim McNeill
- VRML models of Johnson Solids by Vladimir Bulatov
- CRF polychora discovery project attempts to discover CRF polychora Archived 2020-10-31 at the Wayback Machine (
*C*onvex 4-dimensional polytopes with*R*egular polygons as 2-dimensional*F*aces), a generalization of the Johnson solids to 4-dimensional space - https://levskaya.github.io/polyhedronisme/ a generator of polyhedrons and Conway operations applied to them, including Johnson solids.