Question | Answer |
Acute triangle | A triangle in which all three angles are acute Examples: |
Angle | A figure formed by two rays that have a common endpoint Example: |
Chord | A line segment with its endpoints on a circle Example: |
Circle | A closed plane figure with all points on the figure the same distance from the center Example: |
Circumference | The distance around a circle Example: |
Closed figure | A figure that begins and ends at the same point Examples: |
Cone | A solid figure that has a circular base and one vertex Examples: |
Congruent | Having the same size and shape Example: The triangles are congruent. |
Congruent figures | Figures that have the same size and shape Example: The triangles are congruent. |
Coordinate plane | A plane formed by two intersecting and perpendicular number lines called axes Example: |
Coordinates | The numbers in an ordered pair Example: |
Cube | A solid figure with six congruent square faces Examples: |
Cylinder | A solid figure that has two parallel bases that are congruent circles Examples: |
Degree (°) | A unit for measuring angles and temperature Examples: |
Diameter | A line segment that passes through the center of a circle and has its endpoints on the circle Example: diameter |
Dimension | A measure in one direction; the length, width, or height of a figure |
Edge | The line segment where two faces of a solid figure meet Example: edge |
Equilateral triangle | A triangle with three congruent sides Example: |
Face | A polygon that is a flat surface of a solid figure Example: face |
Figurate numbers | Numbers that can be represented by geometric figures Examples: |
Hexagon | A polygon with six sides and six angles Examples: |
Hypotenuse | In a right triangle, the side opposite the right angle; the longest side in a right triangle Example: hypotenuse |
Intersecting lines | Lines that cross at exactly one point Example: Line EF intersects line GH. |
Isosceles triangle | A triangle with two congruent sides Example: |
Line | A straight path in a plane that goes on forever in opposite directions Example: line AB or line BA |
Line segment | A part of a line that includes two points, called endpoints, and all of the points between them Example: line segment AB or line segment BA |
Line symmetry | A figure has line symmetry if a line can separate the figure into two congruent parts Example: |
Obtuse angle | An angle whose measure is greater than 90° and less than 180° Example: |
Obtuse triangle | A triangle that has one obtuse angle Example: |
Octagon | A polygon with eight sides Examples: |
Ordered pair | A pair of numbersthe first number tells how far to move horizontally and the second number tells how far to move vertically |
Parallel lines | Lines in a plane that never intersect Example: |
Parallelogram | A quadrilateral whose opposite sides are parallel and congruent Examples: |
Pentagon | A polygon with five sides Examples: |
Perpendicular lines | Two lines that intersect to form four right angles Example: |
pi (Noun) | The ratio of the circumference of a circle to its diameter An approximate decimal value of pi is 3.14. |
Plane | A flat surface that extends without end in all directions Example: Planes are named by three points in the plane. |
Plane figure | A figure which lies in a plane Examples: |
Point | An exact location in space, usually represented by a dot Example: point A |
Point symmetry | When a figure can be turned half way about a central point and still look the same Example: |
Polygon | A closed plane figure formed by three or more line segments Examples: |
Polyhedron | A solid figure with flat faces that are polygons Examples: |
Prism | A solid figure that has two congruent, polygon-shaped bases, and other faces that are all rectangles Examples: rectangular prism triangular prism |
Protractor | A tool used for measuring or drawing angles Example: |
Pyramid | A solid figure with a polygon base and all other faces triangles that meet at a common vertex Example: This is a square pyramid |
Quadrilateral | A polygon with four sides |
Radius | A line segment with one endpoint at the center of a circle and the other endpoint on the circle Example: radius |
Ray | A part of a line, with one endpoint, that continues without end in one direction Example: ray CD |
Rectangle | A parallelogram with four right angles |