Geometry

Geometry is a branch of mathematics that deals with shapes and their properties - points, lines, planes and solids.

Geometry Terms

  • Acute angle - An angle that measures less than 90°.
  • Adjacent angle - Two angles on a plane having the same vertex and a common line.
  • Angle - Two rays sharing a common point.
  • Angle bisectors - A line that divides an angle into two equal angles.
  • Apex - The vertex at the tip of a cone or pyramid.
  • Apothem - A line segment from the center of a regular polygon to the mid point of a side.
  • Arc length - The distance along the arc or the circumference of a circle or any curve.
  • Area - The inside space of a figure.
  • Base - The bottom of a figure in either plane or solid geometry.  If the bottom and top are parallel then either can be called base.
  • Base area - The base surface area of a solid figure.
  • Center of a circle - A point at a fixed equal distance from all points of the circumference of a circle.
  • Central angle - An angle in a circle with the vertex at the circle's center.
  • Central median -
  • Centroid - The center of a plane or mass.
  • Chord - A line segment on the interior of a circle.
  • Circle segment - An interior part of a circle bound by a chord and an arc.
  • Circumcircle - A circle that passes through all the vertices of a two-dimensional figure.
  • Circumscribed sphere - A polyhedron is a sphere that contains the polyhedron and touches each of the ployhedron's vertices.
  • Circumference - The outside of a circle or a complete circular arc.
  • Concave - An internal angle is greater than 180°.
  • Congruent - All sides having the same lengths. All angles measure the same.
  • Conic section - A section on any plane through a circle, ellipse, hyperbola, and parabola.
  • Convex - No internal angle is greater than 180°.
  • Coplanar - Lines or points lying on the same plane.
  • Diagonal - A line from one vertices to another that is non adjacent.
  • Edge - A line where two or more vertices come together.
  • Ellipsoid - A three-dimensional figure sphere like surface for which all cross sections are ellipses.
  • Foci - Two fixed points on the interior of an ellipse used to define the curve.
  • Focus - The points that construct a conic section.
  • Geometric figure - Any set of points on a plane or in space.
  • Horizontal - Flat or level.
  • Hyporenuse - The side of right triangle opposite the right angle, which is the longest side.
  • Inradius - A circle that touches all lines of a figure.
  • Inscribed angle - An angle inside a circle with its vertex in the circle.
  • Inscribed circle - The largest circle possible that can fit on the inside of a two-dimensional figure.
  • Inscribed sphere - A convex polyhedron is a sphere that is contained within the polyhedron and tangent to each of the polyhedron's faces.
  • Interior angle - An angle on the interior of a plane figure.
  • Lateral surface area - The surface area of a solid figure excluding the area bases of the solid figure.
  • Line - A straight path connecting two points.
  • Line segment (segment) - All points bertween two points.
  • Locus - A word used to define a set of points that form a geometric figure or graph.
  • Median - A line segment from a vertex (corner point) to the midpoint of the opposite side.
  • Midsphere - A polyhedron is a sphere that is tangent to every edge of the polyhedron.
  • Oblique - Tilted at an angle, not horizontal or vertical.
  • Oblique cone - A three-dimensional figure with the apex not alligned above the center at 90° to the base.
  • Oblique cylinder - A three-dimensional figure with both bases not alligned above each other and the center not at 90° to the other base center.
  • Oblique prism - A three-dimensional figure with both bases not alligned above each other and the center not at 90° to the other base center.
  • Oblique pyramid - A three-dimensional figure with the apex not alligned above the center at 90° to the base.
  • Obtuse angle - An angle that measures more than 90°.
  • Outradius (circumcircle) - A circle that touches all corners of an figure.
  • Parallel lines - Two lines that do not intersect.
  • Parallel planes - Two planes that do not intersect.
  • Perimeter - The sum of the lengths of all sides of a plane figure.
  • Perpendicular - At a 90° angle.
  • Perpendicular bisector - A line perpendicular to a segment passing through the segment's midpoint.
  • Plane - An infinate expanse of points in two directions.
  • Point - A single location or the intersection of two lines.
  • Polyhedron - A three-dimensional figure that is a solid with no curved edges or sides.
  • Porportional - Having a constant ratio.
  • Pyramid - A three-dimensional figure that is a polyhedron with a polygonal base and lateral faces that taper to an apex.
  • Quadrilateral - A polygon with four sides.
  • Radius - A line segment between the center point and a point on a circle or sphere.
  • Ray - A line starting at a point and extending infinitely in one direction.
  • Rectangular angle - Two rectangles with different lengths that intersect at a 90° angle at one end each.
  • Regular hexahedron - A three-dimensional figure that is a regular polyhedron where all faces are squares.
  • Regular polygon - A two-dimensional figure that is a polygon where all sides are congruent and all angles are congruent.
  • Regular polyhedron - A three-dimensional figure having faces that are all congruent regular polygons and has dihedral angles that are all congruent.
  • Regular prism - A three-dimensional figure having a base that are regular polygons.  The base is not necessarily aligned one above the other.
  • Regular pyramid - A three-dimensional figure having a base that are regular polygons.  The apex is not necessarily above the center of the base.
  • Regular right prism - A three-dimensional figure having a base that are regular polygons.
  • Regular right pyramid - A three-dimensional figure having a base that are regular polygons.
  • Right angle - A 90° angle.
  • Right cone - A three-dimensional figure with the apex directly above the center at 90° to the base.
  • Right cylinder - A three-dimensional figure with both bases directly above each other and having the centers at 90° to each others base.
  • Right prism - A three-dimensional figure with both bases directly above each other and having the centers at 90° to each others base.
  • Right pyramid - A three-dimensional figure with the apex directly above the center at 90° to the base.
  • Secant line - A line that passes through at least two points on a curve.
  • Sector of a circle - A sector is a fraction of the area of a circle with a radius on each side and an arc.
  • Semiperimeter - One half of the perimeter.
  • Side - Any line segment of an figure.
  • Surface - A three-dimensional figure excluding internal points.
  • Surface area - The total area of all the surfaces of a three dimensional figure.
  • Three-dimensional - A figure with height, width, and depth.
  • Two-dimensional - A flat figure.
  • Vertex - A point where two or more curves, edges, or lines meet.
  • Vertical - Straight up and down.
  • Vertical angles - The opposite angles when two lines intersect.
  • Volume - The amount of space in an solid figure.
Display #
Title
Obtuse Angle
Perpendicular
Pythagorean Theorem
Secant Line
Subtended Angle
Supplementary Angle
Vertex

Subcategories