HOTmaths dictionary

This illustrated dictionary offers free access to over several hundred mathematical symbols, terms and definitions from the early secondary syllabus.

Select any letter to see examples of mathematical terms with clear explanations and helpful diagrams.

The comprehensive glossary of maths terminology is just one of the many special features of the HOTmaths learning system.

To see the complete HOTmaths dictionary, which includes middle secondary and primary maths words, and to investigate all the other components of HOTmaths, get a free account for 7 days.

SYMBOLS A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

To see this feature, you need to subscribe to HOTmaths Unlimited. The HOTmaths Unlimited learning system will also give you access to over 15 000 questions, worksheets and interactives.

   

© 2007 HOTmaths Pty Ltd

Term Definition oblique where a cone or pyramid is slanted in relation to its base The line joining the top to the centre of the base is not perpendicular to the base.

Related links: 3D shapes — Classifying solids 3D shapes — Drawing solids

© 2007 HOTmaths Pty Ltd

Term Definition obtuse-angled triangle a triangle in which one of the angles is an obtuse angle There can only be one obtuse angle in any triangle.

Related links: 2D shapes — Classifying triangles

© 2007 HOTmaths Pty Ltd

Term Definition obtuse angle an angle that measures between 90° and 180°

Related links: 2D shapes — Classifying triangles Angles — How to measure an angle Angles — Types of angles

© 2007 HOTmaths Pty Ltd

Term Definition octagon an eight-sided polygon (with eight angles) A regular octagon has all sides and angles equal. Examples Regular octagon Irregular octagon

Related links: 2D shapes — Plane shapes

© 2007 HOTmaths Pty Ltd

Term Definition octahedron a solid with eight triangular faces A regular octahedron (one of the five Platonic solids) has eight congruent equilateral triangles as faces.

Related links: 3D shapes — Classifying solids 3D shapes — Nets of solids

© 2007 HOTmaths Pty Ltd

Term Definition odd number a whole number that cannot be divided by 2 Example Any number ending in the digits 1, 3, 5, 7, 9. The first 10 odd numbers are 1, 3, 5, 7, 9, 11, 13, 15, 17, 19.

Related links: Number theory — Simple number patterns Number theory — Factors and multiples Number theory — Prime and composite numbers Integers — Dividing integers Algebra — Words into algebra

© 2007 HOTmaths Pty Ltd

Term Definition one-dimensional having one dimension, like a line; requiring one coordinate to specify a point

© 2007 HOTmaths Pty Ltd

Term Definition one whole a single unit; a complete entity Examples 1, 100%, one complete revolution (360°)

Related links: Fractions — Mixed numerals and improper fractions Percentages — One whole is 100% Percentages — Percentage/fraction/decimal connection Applying percentages — Increasing and decreasing using percentages

© 2007 HOTmaths Pty Ltd

Term Definition operation the basic mathematical operations are addition, subtraction, multiplication and division Other operations include powers and roots.

Related links: Whole numbers — Grouping symbols Whole numbers — Order of operations Number theory — Square roots Number theory — Cube roots Integers — Two signs together Integers — Mixing the operations Equations and inequalities — Working backwards Equations and inequalities — A formal approach Manipulating algebra — Reading algebra Manipulating algebra — Formulas in spreadsheets

© 2007 HOTmaths Pty Ltd

Term Definition opposite number a number that is the same distance from zero on the number line as another number, but has a different direction Examples 3 is the opposite number of −3. −7 and 7 are opposites. 1 and −1 are both 1 unit from zero but in different directions.

Related links: Integers — What are directed numbers? Integers — Two signs together

© 2007 HOTmaths Pty Ltd

Term Definition opposite operations arithmetic operations that undo one another (also called inverse operations) Examples Adding and subtracting Multiplying and dividing Squaring and taking the square root

Related links: Number theory — Square roots Number theory — Cube roots Equations and inequalities — Working backwards Equations and inequalities — A formal approach

© 2007 HOTmaths Pty Ltd

Term Definition order of operations a set of rules used to find the value of a mathematical expression Calculate anything in grouping symbols first, next powers, then divisions and multiplications, with subtractions and additions last.

Related links: Whole numbers — Grouping symbols Whole numbers — Order of operations Integers — Mixing the operations Manipulating algebra — Reading algebra

© 2007 HOTmaths Pty Ltd

Term Definition ordered pair two numbers in a specific order used to locate a point on a number plane The ordered pair is usually written inside parentheses: (x-coordinate, y-coordinate) Example C marks the point (−4, −2) in the illustration. The ordered pair marked at D is (2, −4).

Related links: Algebra — Number patterns and pronumerals Algebra — Patterns on the number grid The number plane — Plotting positive integers The number plane — Extending the number plane The number plane — Maps and plans The number plane — Graphs from equations The number plane — Equations from lines The number plane — Comparing lines and equations The number plane — Intersecting lines

© 2007 HOTmaths Pty Ltd

Term Definition origin the point with coordinates (0, 0) on the number plane; the point where the x-axis intersects the y-axis

Related links: The number plane — Plotting positive integers The number plane — Extending the number plane The number plane — Graphs from equations The number plane — Equations from lines The number plane — Comparing lines and equations The number plane — Intersecting lines

© 2007 HOTmaths Pty Ltd

Term Definition outlier in a set of data, any value that is much larger or much smaller than the rest of the data