Welcome to my 'Quick Reference' Geometry Glossary.

This is a list of the most commonly used geometry terms, however it is not exhaustive!

I have created a new, much more comprehensive geometry dictionary for your use. This is an exhaustive list of the geometry terms used by K-6 student AND includes diagrams for over 90% of the entries, so is a great resource for any visual learners!

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2d |
This is an abbreviation of the term Two Dimensional. It is used to describe shapes drawn on a flat surface such as paper which have no volume. |

3d |
This is an abbreviation of the term Three Dimensional. It is used to describe shapes which take up space, ie they have volume. |

Angle |
The distance, measured in degree between two lines. |

Apex |
The highest point of a geometric shahpe. |

Arc, circle |
This is the length of the portion of circumference of the circle created between two radii. |

Area |
The amount of space contained within the perimeter of a shape. |

Block/Box |
The 3d form of a rectangle or square. |

Circle |
A closed curve where all points are an equal distance from the center point. |

Circumference |
A term given to the perimeter of a closed curve. |

Cone |
A 3d shape created by a circular base a triangles. |

Congruent |
Two shapes that are the same size and shape are congruent. |

Cube |
A three dimensional shape created by squares. It has six sides. |

Cylinder |
A 3d shape created by two equal sized circles and lines of equal length connecting them. |

Diameter |
This is the distance from one side of a circle to the other which also goes through the center point. |

Formula |
This is an equation written in the form of X = Y where X is the information you are looking for and Y is the standard calculation including variables required to achieve X. A formula can be difficult to establish, but once established this work does not have to be repeated every time the problem arises. |

Hemisphere |
Half a sphere. |

Hexagon |
A polygon with six sides and six vertices. |

Oblique Cylinder |
A cylinder that does not stand at a right angle from its base. |

Oblique Prism |
A prism that does not stand at a right angle from its base. |

Octagon |
A polygon with eight sides and eight vertices. |

Parallel |
Two or more lines that never touch through infinity. |

Parallelogram |
A four sided figure constructed with two sets of parallel lines. |

Pentagon |
Any five sided polygon. |

Perimeter |
The length of all sides of a polygon added together. |

Perpendicular Height |
This is the height of an object measured from its base to its highest point at an angle 90 degrees. |

Pi |
Pi is a constant in math. It is approximately 3.14159. It is the ratio between a circles circumference and diameter. |

Polygon |
A figure created by any number of straight lines meeting at any angle, that is closed. |

Polyhedron |
A three dimensional shape composed of flat faces with straight edges. |

Prism |
A three dimensional shape composed of two flat faces joined by sides that are perpendicular to them. |

Pyramid |
A three dimensional shape composed of a regular polygon (usually a square) with its face composed of congruent triangles joined at the apex of the pyramid. |

Quadrilateral |
A shape composed of four lines which is closed. |

Radian |
An alternative method of angle measurement. It is equal to 180/π |

Radius |
A line segment of a circle drawn from the center to its perimeter. |

Radii |
The plural form of radius. |

Rectangle |
A quadrilateral shape where opposite sides are equal in length, and all angles are 90 degrees (right angles). |

Rhombus |
A four sided polygon with all four sides equal in length. |

Right Angle |
90 degree angle. |

Sector |
A portion of a circle created by two radii and an arc. |

Semicircle |
A two dimensional shape that is half a circle. Because it is half a circle, the arc of a semi circle always measures 180 degrees. |

Sphere |
A three dimensional shape, where all points on the surface are an equal distance from the spheres center point (radii). The center point of a sphere is not part of the sphere. |

Square |
A polygon composed of four equal sides and angles. |

Surface Area |
Is the amount of an object you can see. A useful way to think of this, is to consider how much material is required to make the shape. |

Trapezoid |
A quadrilateral where two sides are parallel. |

Triangle |
A two dimensional shape composed of three lines of any length, joined at any angle. |

Triangle (right angled) |
A triangle, where two of the line join at 90 degrees. |

Vertex |
A point where two lines of a polygon meet. |

Volume |
How much space a three dimensional shape occupies. A good way to consider volume is to ask, how much water a 3d shape can hold. |

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