Download Geometry Vocabulary Booklet

Geometry
Vocabulary
Booklet
Geometry Vocabulary
Word
Acute
Adjacent
Array
Angle
Axis
Everyday Expression
An angle less than 90 degrees.
Example
Lying next to each other.
Numbers, letter or shapes
arranged in a rectangular
shape.
An angle is a measure of turn –
one full turn is 360 degrees.
Half a turn is 180 degrees.
Quarter turn is 90 degrees.
Labelled horizontal/ vertical
line that marks the edge of a
graph or
co-ordinate grid
Axis of symmetry Same as a line of symmetry.
Base
The base is the face of the
shape that it is resting on.
The base of the cylinder
is a circle
Bisect
To cut in half or cut in two.
The diagonals bisect
each other.
Circle
Semi-Circle
A circle is a two-dimensional
polygon with one side
A semicircle is a twodimensional shape that forms
half of a circle
Circumference
Concave and
Convex
The distance around the circle
(perimeter).
Concave =curving inwards (think
of going into a cave).
Convex
Convex =curving outwards.
Concave
Concentric
Shapes or objects that have
the same centre – so will be
inside each other.
Congruent
If two things are congruent,
they are the same size and
shape (but may be flipped over
in a different position
(orientation).
Corner (see
Vertex)
Where two or more edges/
sides on a shape meet.
A square has 4 vertices.
Cone
A solid (3-D) shape that has a
circular base, 2 faces, 1 edge
and no vertices.
Cube
A solid (3-D) shape that has 6
square faces, 12 edges and 8
vertices. It is a prism.
Cuboid
A solid (3-D) shape that has 6
faces (2 square and 4
rectangular), 12 edges and 8
vertices. It is a prism.
A solid (3-D) shape that has 3
Cylinder
(Cylindrical Prism) faces (2 circles and 1
rectangle) and 2 edges. It has
no vertices. It is a prism.
Diameter
A straight line joining the
edges of a circle that passes
through its centre. The same as
the width of the circle.
Dodecahedron
A solid (3-D) shape that has 12
pentagonal faces, 30 edges and
20 vertices.
Edge
Edges are where two or more
faces meet on a threedimensional shape
e.g. a cube has 12 edges.
Equilateral
Triangle
A triangle with 3 equal sides
and 3 equal angles. It is a
regular polygon.
Face
A face is a flat surface of a
three-dimensional shape
Heptagon
(Septagon)
A polygon with 7 sides. In a
regular heptagon all 7 sides and
7 angles are equal.
Hexagon
A polygon with 6 sides and 6
angles. In a regular hexagon all
6 sides and 6 angles are equal.
e.g. a cube has 6 faces
Isosceles Triangle An irregular 3 sided polygon
with 2 equal sides and 2 equal
angles.
Intersecting/
Intersection
Kite
(Inverted Kite)
Two or more lines that meet at
a point are called intersecting
lines.
A quadrilateral with two pairs
of equal adjacent sides.
Kite
Line of symmetry Any line (real or imaginary) that
divides a shape in two equal
parts, where one part is the
mirror image of the other part.
Inverted Kite
Mirror line
Net
See line of symmetry
A two-dimensional pattern of a
three-dimensional shape that
can be folded to form the
shape.
A net of a cube
Obtuse
A angle that is more than 90
degrees, but less than 180.
Octohedron
A solid (3-D) shape that has 8
triangular faces, 12 edges and 6
vertices.
Octagon
A 2-D polygon with 8 sides and
8 angles. In a regular octagon
all 8 sides and 8 angles are
equal.
Parallel
Two lines equidistant apart
that will never meet.
Rectangles have two
pairs of parallel lines.
Parallelogram
A 2-D quadrilateral with 2 pairs
of parallel lines. Opposite sides
are equal in length.
Pentagon
A 2-D polygon with 5 sides and
5 angles. In a regular pentagon
all 5 sides and 5 angles are
equal.
Perimeter
The distance around the edge
of a shape, or the line that
marks that edge.
3m
4m
The perimeter is
indicted by the thick
black line.
The perimeter is 12m
Perpendicular
Polygon
Two lines that are at right
angles to each other.
A two-dimensional shape which
has three or more straight
sides and no gaps.
Regular polygons have the same
size angles and length of sides
e.g. square
Irregular polygons can have
different lengths of sides and
angles e.g. scalene triangle/
rectangle.
Polyhedron
A solid 3-D shape with flat
faces and straight edges.
Prism
A solid (3-D) shape whose
bases or ends have the same
size and shape and are parallel
to one another.
Pyramid
A solid (3-D) shape with a 2-D
base e.g. triangle/ square/
pentagon etc and triangular
faces which meet at a point.
Quadrilateral
A shape with four straight
edges.
Radius
The distance from the centre
of a circle to its edge.
Rectangle
(Oblong)
A quadrilateral with 4 right
angles; opposite sides are the
same length.
Rhombus
A parallelogram with four equal
sides
Right-Angles
Angle of 90 degrees
Right-Angled
Triangle
A triangle with one right angle.
Scalene Triangle
A triangle with different
length of sides and different
sized angles.
Sphere
A solid (3-D) shape with 1 face,
no edges and no vertices.
Hemisphere
A solid (3-D) shape with a
circular base, 2 faces and 1
edge. It is half a sphere.
A regular quadrilateral, with 4
equal sides and 4 right angles.
It has 4 lines of symmetry.
Square
Symmetrical
Symmetry is when one shape
becomes exactly like another if
you flip, slide or turn it.
The simplest type of Symmetry
is "Reflection" (or "Mirror")
Symmetry
Tangram
A Chinese geometric puzzle
consisting of a square cut into
seven pieces that can be
arranged to make various other
shapes.
Tessellate/
Tessellation
Repeated use of a shape,
without gaps/ overlapping.
Tetrahedron
A triangular based pyramid
consisting of 4 equilateral
faces.
Translation
Moving points/ shapes on a coordinate grid a specified
amount e.g. (4,3)
Trapezium
A quadrilateral with one pair of
parallel lines.
Triangle
A polygon with 3 sides and
internal angles of 180 degrees.
There are 4 types:
Scalene, Right-Angled,
Equilateral and Isosceles.
Venn Diagram
Vertex
Volume
A diagram that allows you to
group items into two or more
categories, some of which
might belong to more than one
category.
Mathematical name for a
corner (vertices is the plural of
vertex).
How much space there is inside
an object, measured in litres of
cubic metres.
A square has 4 vertices,
a cube has 8.
This cube is 2cm x 2cm x
2cm so its volume is 8cm3