Geometry Vocabulary
Glossary terms from Houghton Mifflin Mathematics
- acute angle
- an angle with a measure less than that of a right angle
- angle
- an angle is formed by two rays with the same endpoint
- area
- the number of square units in a region
- base of a geometric figure
- a bottom side or face of a geometric figure
- central angle
- an angle with a vertex at the center of a circle
- chord
- a segment that connects two points on a circle
- circle
- a closed figure in which every point is the same distance from a given point called the center of the circle
- circumference
- the distance around a circle
- cone
- a solid that has a circular base and a surface from a boundary of the base to the vertex
- congruent figures
- figures that have the same size and the same shape
- cube
- a solid figure that has six square faces of equal size
- cylinder
- a solid with two circular faces that are congruent and a cylindrical surface connecting the two faces
- diameter of a circle
- a segment that connects two points on the circle and passes through the center
- edge
- the segment where two faces of a solid figure meet
- endpoint
- the point at either end of a line segment.The beginning point of a ray.
- equilateral triange
- a triangle that has three congruent sides.
- face
- a flat surface of a solid figure
- intersecting lines
- lines that meet or cross at a common point
- isosceles triange
- a triangle that has two congruent sides
- line
- A straight, continous and unending set of points in a plane.
- line of symmetry
- the line along which a figure can be folded so that the two halves match exactly
- line segment
- a part of a line that has two endpoints
- line symmetry
- a figure has line symmetry if it can be folded in half and the two halves are congruent
- obtuse angle
- an angle with a measure greater than that of a right angle and less than 180 degrees
- obtuse triangle
- a triangle that has one obtuse angle
- parallel lines
- lines that lie in the same plane and do not intersect. They are the same distance apart.
- parallelogram
- a quadrilateral in whick both pairs of opposite sides are parallel
- perimeter
- the distance around a figure
- perpendicular lines
- lines that intersect at right angles
- plane
- a flat surface made up of a continous and unending collection of points
- point
- an exact location in space, represented by a dot
- polygon
- a simple closed plane figure made up of three or more line segments
- prism
- a solid figure that has two parallel congruent bases and rectangles and parallelograms for faces
- protractor
- a protractor is a tool used to measure angles in degrees
- pyramid
- a solid figure whose base can be any polygon and whose faces are triangles
- quadrilateral
- a polygon with four sides
- radius
- a segment that connects the center of a circle to any point on the circle
- ray
- Part of a line that starts at an endpoint and goes on forever in one direction.
- rectangle
- a polygon with opposite sides parallel and four right angles
- rectangular prism
- a solid figure with six faces that are rectangles
- rectangular pyramid
- a solid figure whose base is a rectangle and whose faces are triangles
- rhombus
- a parallelogram with all four sides the same length
- right angle
- an angle that measures 90 degrees
- right triangle
- a triangle that has one right angle
- rotational symmetry
- a figure has rotational symmetry if,after the figure is rotated about a point, the figure is the same as when in its original position
- scalene triangle
- a triangle with all sides of different lengths
- side of a polygon
- one of the line segments that make up a polygon
- similar figures
- figures that have the same shape but not necessarily the same size
- solid figure
- a three-dimensional figure in space
- sphere
- a solid figure that is shaped like a round ball
- square
- a polygon with four right angles and four congruent sides
- straight angle
- the measure of a straight angle is equal to 180 degrees
- surface area
- the total area of the surface of a solid
- symmetric figure
- a figure that has symmetry
- symmetry(line symmetry)
- a figure has line symmetry if it can be folded along a line so that the two parts match exactly
- trapezoid
- a quadrilateral with exactly one pair of parallel sides
- triangle
- a polygon with three sides
- triangular prism
- a prism whose bases are triangles
- triangular pyramid
- a pyramid whose base is a triangle
- vertex of an angle
- a point common to the two sides of an angle
- vertex of a polygon
- a point common to two sides of a polygon
- vertex of a prism
- a point common to three sides of a prism
- volume
- the number of cubic units that make up a solid figure