This page gathers the 757 dictionary entries belonging to the domain “Geometry”, as labelled by Wiktionary. Each word leads to its full entry: definitions, etymology, pronunciation, examples. Page 6 of 8: from “polydrafter” to “semimean”.
- polydrafter noun A polyform made by joining N-2 triangles edge to edge in various arrangements, each of these triangles being a right triangle with angles…
- polyform noun A plane or solid figure constructed by joining together identical polygons edge to edge.
- polygon noun A plane figure bounded by edges that are all straight lines.
- polyhedral adj Of, pertaining to or derived from a polyhedron.
- polyhedron noun A solid figure with many flat faces and straight edges.
- polyiamond noun A polyform made by joining one or more equilateral triangles edge to edge in various arrangements, with every polyiamond corresponding to a…
- polyomino noun A plane polyform made by joining one or more squares edge to edge in various arrangements; a similar polyform made from triangles or…
- polytope noun A geometric shape (of any number of dimensions) which is fully enclosed and has flat sides, making it a member of the generalized class of…
- pons asinorum noun A proposition in Euclid stating that the angles at the base of an isoceles triangle are equal.
- porism noun A proposition affirming the possibility of finding such conditions as will render a certain determinate problem indeterminate or capable of…
- power center noun A radical center.
- prism noun An object having the shape of a geometrical prism (sense 1).
- prismoid noun A prismatoid that has planar sides, and the same number of vertices in both of its parallel planes.
- project verb To draw straight lines from a fixed point through every point of any body or figure, and let these fall upon a surface so as to form the…
- projection noun An image of an object on a surface of fewer dimensions.
- projective adj Invariant under projective transformations.
- projective frame noun The projection onto an n − 1 dimensional hyperplane (which is extended so as to be projective) of a set of n + 1 affinely independent…
- projective plane noun A plane in which any pair of distinct points determine a line and any pair of distinct lines intersect at a point.
- projective space noun A kind of geometrical space in which only relation(s) of incidence between points and lines matter; in such a space distances or angles do…
- projective variety noun A Zariski closed subvariety of a projective space; the zero-locus of a set of homogeneous polynomials that generates a prime ideal.
- projectivity noun projective transformation, homography
- projectivization noun A process (more formally, a mapping) that, given a vector space, specifies an associated projective space; (loosely) the projective space…
- proper adj Separated, of finite type, and universally closed.
- proportional noun A proportion.
- prospectivity noun A projective relationship between a line and itself by projecting onto an intersecting line from a point on another line that intersects at…
- prototile noun Any of the minimal set of non-congruent shapes from which a larger set of shapes, some of which may be congruent, can be produced.
- pseudorhombicuboctahedron noun Geometric figure closely related to the rhombicuboctahedron, but differing in the arrangement of its faces; specifically, a Johnson…
- pseudosphere noun A surface generated by rotating a tractrix about its asymptote; a tractricoid
- pyramid noun A solid with triangular lateral faces and a polygonal (often square or rectangular) base.
- pyramidal adj Pyramid-shaped.
- quadrangle noun A geometric shape with four angles and four straight sides; a four-sided polygon.
- quadrant noun One fourth of a circle or disc; a sector with an angle of 90°.
- quadrantal adj Of or relating to a quadrant, or included in the fourth part of a circle.
- quadrate noun A plane surface with four equal sides and four right angles; a square; hence, figuratively, anything having the outline of a square.
- quadrature of the circle noun The problem, proposed by ancient Greek geometers, of using a finite ruler-and-compass construction to make a square with the same area as a…
- quadrilateral noun A polygon with four sides.
- quarter circle noun A quarter of a circle. The shape formed from an arc that is a quarter of the circumference of a circle.
- quasi-projective adj Locally closed with respect to the Zariski topology on projective n-space; isomorphic to such a set.
- quasiregular adj That is semiregular with regular faces of precisely two types that alternate around each vertex.
- r noun Symbol for radius.
- R-pentomino noun A particular five-square polyomino.
- radial adj Of, or relating to a radius (line joining to a geometric centre).
- radian noun In the International System of Units, the derived unit of plane angle: the angle subtended at the centre of a circle by an arc of its…
- radiant noun A straight line proceeding from a given point, or fixed pole, about which it is conceived to revolve.
- radical center noun A point at which the radical lines of three circles meet.
- radio- prefix radius
- radius noun A line segment between any point of a circle or sphere and its center.
- radius vector noun Of a point, a vector going from the origin to that point; equivalently, the transpose of the point.
- rational adj Of a variety: (informally) geometrically simple almost everywhere; (formally) birationally equivalent to projective space
- rational function noun Any function expressible as the quotient of two (coprime) polynomials (and which thus has poles at a finite, discrete set of points which…
- real projective plane noun A three-dimensional vector space over the field of real numbers in which one-dimensional linear subspaces are considered as “points” and…
- reciprocal lattice noun A conceptual lattice in reciprocal (or momentum) space that corresponds to a given Bravais lattice in realspace.
- rectangle noun Any quadrilateral having opposing sides parallel and four right angles.
- rectangular cuboid noun A special case of a cuboid with rectangular faces in which all of its dihedral angles are right angles.
- rectification noun The determination of a straight line whose length is equal to a portion of a curve.
- rectilinear adj Formed from straight lines.
- reflex adj Having greater than 180 degrees but less than 360 degrees.
- regular adj Both equilateral and equiangular; having all sides of the same length, and all (corresponding) angles of the same size
- regular map noun A morphism between algebraic varieties.
- regular polygon noun A polygon which is both equiangular and equilateral (i.e. having all sides the same length and all interior angles the same).
- reptation noun The motion of one plane figure around another, so that the longest diameter of one shall come into line with the shortest of the other.
- rhombic dodecahedron noun A convex polyhedron that has 12 congruent rhombic faces, 24 edges and 14 vertices of two types (eight 3-edge and six 4-edge) and is a…
- rhombic triacontahedron noun A convex polyhedron that has 30 congruent rhombic faces, 60 edges and 32 vertices of two types (twenty 3-edge and twelve 5-edge) and is the…
- rhombicosidodecahedron noun An Archimedean solid with 62 regular faces (20 triangles, 30 squares, and 12 pentagons), 60 vertices and 120 edges.
- rhombicuboctahedron noun An Archimedean solid with eight triangular and eighteen square faces; the small rhombicuboctahedron.
- rhombitrihexagonal adj Relating to a semiregular tiling of the Euclidean plane with one triangle, two squares, and one hexagon on each vertex.
- rhombus noun A parallelogram having all sides of equal length.
- Riemannian geometry noun The branch of differential geometry that concerns Riemannian manifolds; an example of a geometry that involves Riemannian manifolds.
- right adj Of an angle, measuring 90 degrees, or one quarter of a complete rotation; the angle between two perpendicular lines.
- right angle noun Half of the angle formed by a single straight line, equivalent to 90 degrees.
- rigidification noun A form of isomorphism applied between line bundles.
- ring noun A planar geometrical figure included between two concentric circles.
- roll verb To apply (one line or surface) to another without slipping; to bring all the parts of (one line or surface) into successive contact with…
- rotation noun An operation on a metric space that is a continuous isometry and fixes at least one point.
- rotunda noun A form of cupola that has pentagons rather than squares or rectangles.
- roulette noun The locus of a point on a plane curve that rolls without slipping along another fixed plane curve.
- ruled adj Being a scroll; being such that through every point of S there is a straight line that lies on S.
- runcination noun An operation in any dimension that cuts a regular polytope at its faces, its edges and its vertices, creating a new facet in place of each…
- Rupert adj Having or relating to the property of being able to pass through a copy of itself.
- saddle noun Synonym of saddle point (“a point in the range of a smooth function, every neighbourhood of which contains points on each side of its…
- saddle point noun A point in the range of a smooth function, every neighbourhood of which contains points on each side of its tangent plane.
- sagitta noun The distance from a point in a curve to the chord; also, the versed sine of an arc; so called from its resemblance to an arrow resting on…
- salient adj Denoting any angle less than two right angles.
- scalebound adj Of an object: for which characteristic elements of scale, such as length and width, are few in number and each with a clearly distinct size.
- scalenohedron noun A polyhedron having twelve sides, each in the form of a scalene triangle, that is topologically equivalent to a hexagonal bipyramid and…
- scheme theory noun The branch of mathematics that concerns schemes (locally ringed spaces admitting coverings by open sets, each isomorphic to the spectrum of…
- Schiffler point noun A certain type of triangle center. A triangle △ABC with the incenter I has its Schiffler point at the point of concurrence of the Euler…
- Schläfli double six noun A configuration of 30 points and 12 lines. The lines can be partitioned into two subsets of six: each line is disjoint from (skew with) the…
- Schläfli symbol noun A notation that recursively encodes certain properties of a specified regular polytope or tessellation.
- Schlegel diagram noun A projection of a polytope from n-dimensional space to n-1 dimensions through a point beyond one of its faces; especially such a projection…
- Schönhardt polyhedron noun The simplest non-convex polyhedron that cannot be triangulated into tetrahedra without adding new vertices.
- scissor congruence noun The property of two polygons that have the property of being decomposable into finitely many polygons that are pairwise congruent.
- scroll noun A skew surface.
- secant noun A straight line that intersects a curve at two or more points.
- sector noun Part of a circle, extending to the center; circular sector.
- segment noun The part of a circle between its circumference and a chord (usually other than the diameter).
- semiangle noun an angle of half a given size
- semimajor adj Of or pertaining to the semimajor axis, the long axis of an ellipse
- semimajor axis noun Half of the major axis of a circle or ellipse.
- semimean adj Pertaining to half the length of the middle axis on an ellipse (halfway between the major and minor axes).