GLOSSARY 313reflective symmetry A shape
has reflective symmetry if you
can draw a line through it to
make two halves that are
mirror images of each other.reflex angle An angle
between 180 and 360 degrees.remainder The number
that is left over when one
number doesn’t divide into
another exactly.rhombus A quadrilateral with
all four sides the same length.
A rhombus is a special kind of
parallelogram, in which all the
sides are of equal length. See
parallelogram.right angle An angle of
90 degrees (a quarter turn),
such as the angle between
vertical and horizontal lines.right-angled triangle
A triangle where one of the
angles is a right angle.rotation Turning around a
central point or line.rotational symmetry A shape
has rotational symmetry if it
can be turned around a point
until it fits exactly into its
original outline.rounding Changing a number
to a number, such as a
multiple of 10 or 100, that’s
close to it in value and makes
it easier to work with.scalene triangle A triangle
where none of the sides or
angles are the same size.sector A slice of a circle similar
in shape to a slice of cake. Its
edges are made up of two
radii and an arc.segment (1) Part of a line.
(2) In a circle, the area
between a chord and the
circumference.sequence An arrangement of
numbers one after the other
that follows a set pattern,
called a rule.set A collection or group of
things, such as words,
numbers, or objects.significant digits The digits
of a number that affect its
value the most.simplify (a fraction) To put a
fraction into its simplest form.
For example, you can simplify(^14) ⁄ 21 to (^2) ⁄ 3.
solid In geometry, a term for
any 3D shape, including a
hollow one.
sphere A round, ball-shaped
3D shape, where every point
on its surface is the same
distance from the centre.
square A four-sided 2D
shape where all the sides
are the same length and all
the angles are 90 degrees.
A square is a special kind of
rectangle. See rectangle.
square number If you multiply
a number by itself, the result is
called a square number, for
example 4 × 4 = 16
square unit Any unit for
measuring the size of a flat
area. See unit.
straight angle An angle of
exactly 180 degrees.
subset A set that is part of
a larger set. See set.
symmetry A shape or object
has symmetry if it looks exactly
the same after a reflection
or rotation.
tally marks Lines drawn to
help record how many things
you’ve counted.
tangent A straight line that
just touches a curve or the
circumference of a circle at
a single point.
three-dimensional (3D)
Having length, width, and
depth. All solid objects are
three-dimensional – even
very thin paper.
ton/tonne A tonne is a metric
unit of mass equal to a
thousand kilograms: it is also
called a metric ton. A ton is
also a traditional imperial unit,
which is almost the same size
as a tonne.
transformation Changing the
size or position of a shape or
object by reflection, rotation,
or translation.
translation Changing the
position of a shape or object
without rotating it or changing
its size or shape.
trapezium A quadrilateral
with one pair of sides parallel,
also called a trapezoid.
triangle A 2D shape with three
straight sides and three angles.
turn To move round a fixed
point, such as hands moving
on a clock.
two-dimensional (2D)
Having length and width, or
length and height, but no
thickness.
unit A standard size used for
measuring, such as the metre
(for length) or the gram (for
mass).
unit fraction A fraction in
which the numerator is 1, for
example^1 ⁄ 3.
universal set The set that
includes all the data you’re
investigating. See set.
value The amount or size
of something.
variable An unknown number
in an equation. In algebra, a
variable is usually represented
by a letter or a shape.
Venn diagram A diagram that
shows sets of data as
overlapping circles. The
overlaps show what the
sets have in common.
vertex (plural vertices)
An angled corner of a 2D
or 3D shape.
vertical Going in a straight up
and down direction.
volume The three-dimensional
size of an object.
weight A measurement of the
force of gravity acting on an
object. See mass.
whole number Any number
such as 8, 36 or, 5971 that is
not a fraction.
x axis The horizontal line that
is used to measure the
position of points plotted on
a grid or graph.
y axis The vertical line that is
used to measure the position
of points on a grid or graph.
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