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Lists of shapes
Lists of shapes
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Small and great stellated dodecahedron from Harmonices Mundi by Johannes Kepler

Lists of shapes cover different types of geometric shape and related topics. They include mathematics topics and other lists of shapes, such as shapes used by drawing or teaching tools.

Mathematics

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from Grokipedia
Lists of shapes encompass organized compilations of geometric figures across mathematical, natural, scientific, cultural, and applied contexts, systematically categorized by dimensionality—such as two-dimensional (2D) and three-dimensional (3D)—and further subdivided based on attributes like the number of sides, regularity, convexity, and . These lists serve as foundational references for studying spatial relationships, symmetries, and topological properties, aiding in the classification of polygons (flat-sided 2D shapes with straight edges) and (solid 3D shapes bounded by polygons). Broader enumerations extend to biological forms, astronomical bodies, artistic symbols, and industrial designs. In two dimensions, common lists include triangles (three-sided polygons, classified as equilateral, isosceles, scalene, or right-angled), quadrilaterals (four-sided figures like squares, rectangles, rhombuses, parallelograms, and trapezoids), and higher-sided polygons up to n-gons, alongside curved shapes such as circles and ellipses. Regular polygons, where all sides and angles are equal, form a key subset, with examples ranging from the to the regular and beyond. Concave and convex variants further refine these classifications, emphasizing interior angle sums and side alignments. Three-dimensional lists extend to polyhedra, prominently featuring the five Platonic solids—tetrahedron, , , , and —which are regular polyhedra with identical regular polygonal faces meeting at each vertex. Additional categories include Archimedean solids (13 semi-regular polyhedra with regular faces of two or more types, uniformly arranged) and Johnson solids (92 strictly convex polyhedra with regular faces but irregular vertex figures). Curved 3D shapes, such as spheres, cylinders, cones, and tori, complement these, focusing on surfaces generated by rotating 2D profiles. Beyond basic dimensions, advanced lists explore higher-dimensional analogs, like four-dimensional polytopes (e.g., the or ) and space-filling polyhedra that tessellate three-dimensional space without gaps, such as the or . These enumerations underpin applications in architecture, , crystallography, and physics, where shape properties inform structural stability, visual modeling, and molecular configurations. Overall, lists of shapes provide a structured framework for geometric exploration, evolving from Euclidean foundations to modern computational classifications.

Mathematical Shapes

Two-Dimensional Shapes

Two-dimensional shapes, or plane figures, are geometric objects confined to a flat surface without depth, fundamental to as established in ancient texts. Euclid's Elements, composed around 300 BCE, laid the axiomatic foundations for these shapes through definitions, postulates, and theorems, systematizing earlier Greek contributions from figures like Eudoxus and Theaetetus. In Books I–IV and VI, Euclid defined basic plane elements such as points, lines, angles, triangles, and circles, enabling deductive proofs of their properties and influencing mathematical development for over two millennia. Polygons represent a primary class of two-dimensional shapes, defined as closed plane figures formed by three or more straight line segments (sides) connecting vertices, with no three successive points collinear. They are classified by the number of sides (n-gon), regularity (equal side lengths and interior angles for regular polygons; unequal otherwise), and convexity (all interior angles less than 180° for convex; at least one greater for concave). The sum of interior angles in an n-gon is (n-2) × 180°. Common polygons include triangles (3 sides), quadrilaterals (4 sides), and pentagons (5 sides), with names for higher-sided figures as follows:
Number of Sides (n)Polygon Name
3Triangle
4Quadrilateral
5Pentagon
6Hexagon
7Heptagon
8Octagon
9Nonagon
10Decagon
Curved two-dimensional shapes contrast with polygons by featuring smooth, non-linear boundaries. A circle is the set of all points in a plane equidistant from a fixed center point (radius r), with Cartesian equation (xx0)2+(yy0)2=r2(x - x_0)^2 + (y - y_0)^2 = r^2 for center (x0,y0)(x_0, y_0). An ellipse is the locus of points where the sum of distances to two fixed foci (separated by 2c) equals a constant 2a (semimajor axis), parameterized as x=acostx = a \cos t, y=bsinty = b \sin t where bb is the semiminor axis and b2=a2c2b^2 = a^2 - c^2. A parabola is the set of points equidistant from a fixed point (focus) and line (directrix), with standard equation y2=4axy^2 = 4ax for a right-opening form with vertex at the origin. Among non-convex polygons, star polygons (also called stellated polygons) form self-intersecting figures by connecting every q-th point among p equally spaced points on a , denoted {p/q} where gcd(p,q)=1 and q < p/2. The {5/2} is a classic example, appearing as a . Irregular polygons deviate from regularity without self-intersection, such as scalene triangles or arbitrary quadrilaterals, while star polygons like the {6/2} () exhibit density q in their winding. Tessellations, or tilings, cover the plane without gaps or overlaps using two-dimensional shapes, classified by tile regularity and arrangement. Regular tessellations use identical regular polygons meeting edge-to-edge, limited to three types: equilateral triangular, , and regular hexagonal grids. Semi-regular (Archimedean) tessellations employ two or more regular polygons with identical vertex configurations, yielding eight distinct types, such as the snub . Aperiodic tessellations, like Penrose tilings using rhombi with angles of 36° and 144°, fill the plane without periodic repetition, discovered in the 1970s and notable for their quasi-crystalline order. These plane figures provide the basis for higher-dimensional extensions, such as extruding to form prisms in three dimensions.

Three-Dimensional Shapes

Three-dimensional shapes, or solid figures in , encompass with flat polygonal faces and curved surfaces such as spheres and cylinders. These shapes are fundamental in , with further classified by their regularity and uniformity, while curved solids are defined by quadratic equations and possess and surface area formulas derived from integration or classical methods. satisfy for convex cases, VE+F=2V - E + F = 2, where VV is the number of vertices, EE the edges, and FF the faces. The Platonic solids represent the most symmetric convex polyhedra, consisting of five regular types where all faces are identical regular polygons and the same number of faces meet at each vertex. These are the (4 triangular faces), (6 square faces), (8 triangular faces), (12 pentagonal faces), and (20 triangular faces). Their vertex, edge, and face counts are summarized below, all verifying :
SolidFaces (F)Vertices (V)Edges (E)
446
6812
8612
122030
201230
Beyond Platonic solids, Archimedean solids comprise 13 convex uniform polyhedra featuring regular polygonal faces of two or more types, with identical vertex configurations. Examples include the (4 regular hexagons and 4 equilateral triangles), (8 triangles and 6 squares), (8 triangles and 6 octagons), (18 squares and 8 triangles), and (32 triangles and 6 squares). These solids are vertex-transitive but not face-transitive, distinguishing them from Platonic solids. Johnson solids extend this classification with 92 strictly convex polyhedra that have regular polygonal faces and equal edge lengths, excluding the Platonic solids, Archimedean solids, prisms, and antiprisms. Representative examples include the (J1: 1 square and 4 triangles), (J2: 1 pentagon and 5 triangles), triangular cupola (J3: 1 triangle, 1 hexagon, 3 squares, and 9 triangles), and gyroelongated square dipyramid (J17: 16 triangles and 2 squares). These were enumerated by Norman Johnson in 1966, providing a complete catalog of such non-uniform convex polyhedra. Convex uniform polyhedra encompass the 5 Platonic solids and 13 Archimedean solids as the finite set, alongside infinite families of prisms and antiprisms that share regular faces and transitive vertices. Prisms are polyhedra with two parallel congruent n-gonal bases connected by n rectangular lateral faces, such as the (2 triangles and 3 rectangles) or (2 pentagons and 5 rectangles). Antiprisms feature two parallel n-gonal bases rotated relative to each other, linked by 2n equilateral triangular faces, exemplified by the (2 squares and 8 triangles) or octahedral antiprism (which coincides with the ). Pyramids consist of an n-gonal base and n triangular lateral faces converging at an apex, like the (1 square and 4 triangles) or (1 and 6 triangles). These forms highlight the diversity of uniform and semi-regular structures in three dimensions. Space-filling polyhedra are convex polyhedra that can tessellate three-dimensional without gaps or overlaps. Notable examples include the and the , the latter forming the Kelvin structure. There are infinitely many such polyhedra, but only 28 combinatorially distinct types of tetrahedra, octahedra, and cuboctahedra that fill uniformly. Curved three-dimensional shapes include the , defined by x2+y2+z2=r2x^2 + y^2 + z^2 = r^2, with surface area 4πr24\pi r^2 and 43πr3\frac{4}{3}\pi r^3. Cylinders have circular bases and rectangular lateral surfaces, governed by the equation x2+y2=r2x^2 + y^2 = r^2 (independent of z for infinite extent), yielding πr2h\pi r^2 h and total surface area 2πr(r+h)2\pi r (r + h) for height h. Cones taper from a circular base to an apex, with 13πr2h\frac{1}{3}\pi r^2 h and lateral surface area πrr2+h2\pi r \sqrt{r^2 + h^2}
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