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Geometry Vocabulary

geometry terms

Acute Angle An angle with a measure greater than 0 degrees but less than 90 degrees.
Acute Triangle A triangle with three acute angles
Angle Two rays that share an endpoint (vertex)
Area The amount of surface in a region or enclosed within a boundary.
Circle A closed curve with all points an equal distance from the center
Circumference The distance around the outside of a circle.
Cone A three-dimensional figure with a circular base joined to a vertex by a curved surface.
Congruent Having exactly the same size and shape.
Cube A solid figure in which every face is a square and every edge is the same length.
Decagon A polygon with ten sides.
Diameter A line segment that cuts a circle in half.
Endpoint The point(s) at the end of a ray or line segment.
Equilateral Triangle A triangle with three congruent sides. Each angle measures 60 degrees.
Flip another word for REFLECTION
Geometry The branch of mathematics that deals with the position, size, and shape of figures.
Hemisphere Half of a sphere
Heptagon A polygon with seven sides.
Hexagon A polygon with six sides.
Isosceles Triangle A triangle with at least two congruent sides and two congruent angles.
Kite A convex quadrilateral with two distinct pairs of adjacent, congruent sides.
Line A set of points that form a straight path extending infinitely in two directions.
Line of Symmetry A line dividing a two-dimensional figure into two parts that are mirror images of each other.
Line Segment A part of a line. A line segment has two endpoints and a definite length.
Nonagon A polygon with nine sides.
Obtuse Angle An angle that is greater than 90 degrees but less than 180 degrees
Obtuse Triangle A triangle that has one obtuse angle.
Octagon A polygon with eight sides.
Parallel Lines Lines lying in the same plane that are always the same distance apart.
Parallelogram A quadrilateral with both pairs of opposite sides parallel. Opposite angles are congruent.
Pentagon A polygon with five sides.
Perimeter The distance around a figure.
Perpendicular At right angles.
Plane A flat surface extending infinitely in all directions.
Point The smallest geometric unit. A position in space, often represented by a dot.
Polygon A simple, closed, plane figure bounded by straight sides.
Quadrilateral A polygon with four sides.
Ray A set of points that form a straight path extending infinitely in one direction. A ray has one endpoint.
Rectangle A parallelogram with four right angles. Opposite sides are congruent and parallel.
Reflection A transformation of a geometric figure that results in a mirror image of the original.
Regular Polygon A polygon that has equal sides and equal angles.
Rhombus A parallelogram with four congruent sides. Opposite angles are congruent.
Right Angle An angle that is one-fourth of a full turn. A right angle measures 90 degrees.
Right Triangle A triangle that has one right angle.
Scalene Triangle A triangle with no sides congruent.
Similar Figures that have the same shape but not necessarily the same size.
Slide another word for TRANSLATION
Sphere A three-dimensional figure formed by a set of points that are all the same distance from a fixed point called the center.
Square A rectangle with congruent sides.
Symmetry If a figure can be folded along a line so that the two halves match exactly, then the figure has line symmetry.
Three-Dimensional Relating to objects that have length, width, and depth. Solid figures such as polyhedra, cones, and spheres are three-dimensional.
Translation A transformation in which a geometric figure is formed by moving every point on a figure the same distance in the same direction.
Trapezoid A quadrilateral with exactly one pair of parallel sides.
Triangle A polygon with three sides.
Triangular Prism A prism in which the bases are triangles.
Two-Dimensional Relating to figures that have length and width but not depth. Figures such as polygons and circles are two-dimensional.
Vertex A point at which two line segments, lines, or rays meet to form an angle.
Created by: PRO Teacher lit123