Glossary
There are several hundred words or expressions that relate to your child's primary school numeracy work, but there are lots of terms that are used in everyday language (such as quarter-to, biggest, litre etc), as well as those that most parents are already familiar with (such as vertical, approximate, octagon etc). However there are likely to be some words which you have forgotten the meaning of, or terms that may be new to you. We have therefore put together this glossary to help.
You can also find a link to an online, interactive glossary at the bottom of this page, as well as visual descriptions of the different forms of diagrams, graphs and charts referrred to in the glossary.
Acute angle - An angle between 0 and 90 degrees.
Angle - The space (usually measured in degrees) between two intersecting lines at the point where they meet.
Area - A measure of surface - area is usually measured in square units e.g. square centimetres.
Array - An ordered collection of counters, numbers etc. in rows and columns.
Axis - The labelled horizontal or vertical line that marks the edge of a graph.
Bar chart - A way of representing statistical information. Bars, of equal width, represent frequencies and the lengths of the bars are proportional to the frequencies. Sometimes called bar graph.
Carroll diagram - A sorting diagram named after Lewis Carroll, author and mathematician.
Chunking - A method for dividing by subtracting 'chunks' or groups of the divisor from the dividend.
Circumference - The distance round the edge of a circle (its perimeter).
Decimal fraction - Any fraction where the bottom number (denominator) is 10, 100, 1,000 or higher power of 10. These fractions can be represented as digits following a decimal point. The decimal point is placed at the right of the units column. Each column after the decimal point is a decimal place. Example: The decimal fraction 0.325 is said to have three decimal places.
Denominator - In the notation of common fractions, the number written below the line i.e. the divisor.
Distribution - The pattern formed by a set of data. This pattern is usually most easily seen when the data is plotted in a graph or chart.
Dividend - In a calculation A divided by B, A is known as the dividend.
Divisor - In the calculation A divided by B, B is known as the divisor.
Equilateral triangle - A triangle whose three sides are the same length (and whose three angles are each 60 degrees)
Face - One of the flat surfaces of a solid shape. Example: a cube has six faces. Factor - A whole number that divides exactly into another number. Example: 1, 2, 4, 5, 10 and 20 are all factors of 20.
Fraction, improper/vulgar/proper - A vulgar, or common, fraction is any number represented as one whole number divided by another whole number (e.g. ¾). The fraction is called 'improper' if the top number (numerator) is larger than its bottom number (denominator), otherwise it is called 'proper'.
Frequency chart - A table recording data and how frequently things occur. Tallies are often used to record frequencies.
Grid method - A method of teaching multiplication in primary school, as a precursor to teaching the traditional long multiplication method.
HTU - An acronym for a three-digit number (Hundreds Tens Units).
Integer - Any of the positive or negative whole numbers and zero. Example: -6, -1, 0, +3, +9
Isosceles triangle - A triangle in which two sides have the same length and consequently two angles are equal.
Lowest common multiple - If you have two or more whole numbers, their lowest common multiple if the smallest number into which both of the number can exactly divide. Example: The lowest common multiple of 6 and 15 is 30.
Mean - The most common form of average, calculated by finding the total of a group of numbers and then dividing by the number in the group. Example: The mean of 2, 4, 4, 5, 8, 9, 9 is 2 + 4 + 4 + 5 + 8 + 9 + 9 divided by 7 (the number of numbers in the group).
Median - One way of expressing the average - the median is the middle value if all the items are listed in order from smallest to largest. Example: The median of 2, 4, 4, 5, 8, 9, 9 is 5, the middle number.Mixed number - A number expressed as a whole number and a fraction, e.g. 1¾.
Mode - Another way of expressing an average, the mode is the measurement that occurs most frequently. Example: The modal number of fingers on a human being is 10.
Multiple - The result of multiplying a whole number by another whole number.
Number bonds - All pairs of numbers with a particular total, e.g. number bonds to ten are all pairs of whole numbers with the total 10.
Number line - A line where counting numbers are represented by points upon it, used to help children to learn addition and subtraction.
Obtuse angle - An angle greater than 90 but less than 180 degrees
Partitioning - To split a number into component parts. Example: the two-digit number 42 can be partitioned into 40 + 2 or 21 + 21.
Percentage - A fraction expressed as the number of parts per hundred and recorded using the notation %. Example: One half can be expressed as 50%; the whole can be expressed as 100%.
Perimeter - The length of the boundary of a closed figure.
Perpendicular - Two lines that are at right angles to each other.
Pie Chart - A circular chart used to display the relative proportions of a group that had a particular feature.
Place value - The value of a digit that relates to its position or place in a number. Example: in 2736 the digits represent 2 thousand, 7 hundreds, 3 tens and 6 units respectively; in 16.87 the digits represent 1 ten, 6 units, 8 tenths and 7 hundredths respectively.
Prime number - A whole number greater than 1 that has exactly two factors, itself and 1. Examples: 2 (factors 2, 1), 3 (factors 3, 1). 51 is not prime (factors 51, 17, 3, 1).
Probability - The likelihood of an event happening. Probability is expressed on a scale from 0 to 1. Where an event cannot happen, its probability is 0 and where it is certain its probability is 1.
Product - The result of multiplying one number by another.
Reflex angle - An angle that is greater than 180 but less than 360.
Right angle - When the angle between two straight lines that meet is 90 degrees.
Scalene triangle - A triangle with no two sides equal and consequently no two angles equal.
Subtraction by decomposition - A vertical method of subtraction. The number in the top line is broken down to aid calculation.
Venn diagram - A diagram that allows you to group items into two or more categories, some of which might belong to more than one category.
Vertex - The mathematical name for a corner, the point at which two or more lines intersect. Plural: vertices.
Useful links
Interactive glossary with examples
Graphs and charts used to display data
(I have this as a PDF document which can be used for the website, but I don't know how to embed it into a blog!)
