Learning math is like learning a foreign language. In order to be successful in Math, students must become fluent with the vocabulary. To help children learn Math in a language that is not their first language, teachers and parents need to assess whether this is desirable and attempt to find meaningful, effective ways in which they are able to correctly use Mathematical terms and apply them to problemsolving.
As many parents have realized that throughout the time studying Math in English, your child will be introduced to a huge number of words and phrases, many of which may seem baffling – both to them and to you.
In this article, we list down the most important Math vocabulary words and concepts that every primary student should know. This list is designed to inform students, parents, and teachers of the vocabulary and meaning of terms in mathematics that students may have encountered in their primary school, in international Math contests, Math online learning sites… and will encounter when they transfer to postprimary education.
Please note that this is not a comprehensive glossary of every basic mathematical term that could come up throughout your child’s primary school life, merely the key ones they will need to form solid foundations in the subject.
Term  Definition  Diagram/ Example  
A  Addends  Numbers involved in an addition problem; a number that is added to another number  
Addition  Finding the total, or sum, by combining two or more numbers.  
Acute angle  An Acute Angle is less than 90°  
Angle  The amount of turn between two lines around their common point (the vertex).  
Ascending order  Arranged from smallest to largest. Increasing.  2, 4, 15, 31 are in ascending order.  
Area  The size of a surface.  
Average  A calculated “central” value of a set of numbers.  
B  Bar chart  A bar chart is a form of a graph that displays information using rectangular bars to show value.  
Bar model  A bar model is a method that uses diagrams of rectangular bars to represent maths problems in a visual way  
C  Circle  A continuous curved line, the points of which are always the same distance from the center point.  
Circumference  The distance around the edge of a circle.
Circumference of Circle = 2πr 

Complementary angles  Two angles are complementary angles when they add up to 90°  
Composite number  A whole number that can be made by multiplying other whole numbers.  
Cone  A solid (3dimensional) object that has a circular base joined to a point by a curved side.
The pointed end of the cone is called the apex, whereas the flat surface is called the base. 

D  Decimal  A decimal number (based on the number 10) contains a Decimal Point. 
“fortyfive and sixtenths” written as a decimal number 
Decline  to gradually become less, lower  
Decomposing number  Decomposing is when we break the number apart  
Descending order  Arranged from largest to smallest. Decreasing.  For example, 210, 52, 11, 9, 2 are in descending order.  
Denominator  The bottom number in a fraction.  
Diagonal  A line that goes from one corner to another, but is not an edge.  
Diameter  The distance from one point on a circle through the center to another point on the circle. And it is twice the radius.  
Difference  The difference means to subtract one value from another  
Dividend  The number that you want to divide up.  
Divisible  When dividing by a certain number gives a whole number answer  For example, 10 is divisible by 5, because 10 ÷ 5 = 2 exactly
But 9 is not divisible by 2 because 9 ÷ 2 is 4 with 1 leftover. 

Division  The division is splitting into equal parts or groups.  
Divisor  The number we divide by.  
E  Edge  An edge is a name for lines created when two faces in a 3D shape meet.  
Equal  Exactly the same amount or value  
Even number  Any integer that can be divided exactly by 2 is an even number.  
Equation  A mathematical statement shows that both sides equal the other.  For example, 12 – 5 = 3 + 4  
Equilateral triangle  A triangle with three equal sides and three equal angles.  
Equivalent fraction  The fractions that have different numerators and denominators but are equal to the same value.  
F  Factor  Numbers we can multiply together to get another number.  For example, 2, 3, 4, and 6 are all factors of 12, and 12 can be divided into them exactly. 
Fewer  Smaller quantity or amount.  
Fraction  Shows how many parts of a whole:
• the top number (the numerator) says how many parts we have. • the bottom number (the denominator) says how many equal parts the whole is divided into 

G  Geometry  The branch of mathematics that deals with points, lines, shapes, and space.  
Greater  Bigger.
The symbol > means greater than 
For example, 7 > 4 shows that 7 is greater than 4.  
H  Hypotenuse  The side opposite the right angle in a rightangled triangle.  
Hemisphere  A hemisphere is a halfsphere formed by a plane intersecting the center of a sphere.  
Hexagon  A hexagon is a 6sided polygon  
I  Increase  Make something bigger (in size or quantity).  
Integer  A whole number. It may be positive, negative, or zero.  
Isosceles triangle  A triangle with two equal sides and two equal angles across from them.  
L  Less than  Smaller.
The symbol < means less than 
For example, 4 < 7 shows that 4 is less than 7. 
Line  A line is absolutely straight, has no thickness, extends in both directions without end.  
M  Mean  Found by adding a set of values and dividing the total by the number of values in the set.  For example, the mean of 2, 4, 5, 7 and 12 is 6 because (2 + 4 + 5 + 7 + 12) ÷ 5 = 6 
Median  The median of a set of numbers is the middle number in that list. The numbers in the list must first be sorted into ascending order.  For example, the median of 1, 2, 3, 4, 5, 6, 7 is 4.  
Midpoint  The middle point of a line segment.  
Minuend  The first number in a subtraction.  
Mixed number  A whole number and a fraction combined  For example, 5½ (five and a half) is a mixed number.  
Mode  The mode of a set of numbers is the one that appears most often.  For example, the mode of 2, 3, 4, 5, 5, 6, 7 is 5.  
Multiple  A multiple is a result of multiplying one integer by another.  
Multiplication  The basic idea of multiplication is repeated addition.  For example: 5 × 3 = 5 + 5 + 5 = 15  
N  Negative number  Less than zero.  
Numerator  The top number in a fraction.  
Number line  A number line is a horizontal line, with numbers placed at equal or segments along its length.  
O  Obtuse angle  An Obtuse Angle is more than 90° but less than 180°  
Odd number  Any integer that cannot be divided exactly by 2 is an odd number.  
P  Pair  Two together.  For example, {12,11} is a pair of numbers 
Parallel  2 lines that always have the same distance apart and never touching.  
Parallelogram  A Parallelogram is a flat shape with opposite sides parallel and equal in length.  
Pentagon  A pentagon is a 5sided Polygon  
Percentage  Percentage means ‘out of 100’ and is used to show a number or ratio expressed as a fraction of 100.  For example, this 300.000VND jacket had 20% off in the Christmas sale.  
Perimeter  The total distance around the outside of a polygon. This distance is obtained by adding together the units of measure from each side.  For example, the perimeter of this rectangle is 7+3+7+3 = 20  
Perpendicular  Two lines or line segments intersecting to form a right angle.  
Polygon  A polygon is any 2D shape with straight, closed sides.  
Prime number  A prime number is any number greater than 1 that can only be divided equally by itself and 1.  
Prism  A prism is a 3D shape with two identical flat sides and ends.  
Product  The answer when two or more values are multiplied together.  
Q  Quotient  The answer after we divide one number by another.  For example, in 12 ÷ 3 = 4, 4 is the quotient. 
Quadrilateral  A flat shape with four straight sides.  
R  Radius  The distance from the center to the circumference of a circle  
Ratio  A ratio shows the relative sizes of two or more values.  For example, the ratio of boys to girls was 2:1, meaning there are two boys for every one girl.  
Remainder  An amount left over after division  
Right angle  A right angle is an internal angle which is equal to 90°  
Rhombus  A Rhombus is a flat shape with 4 equal straight sides.  
S  Scalene triangle  No equal sides
No equal angles 

Sequence  A sequence is a list of things (usually numbers) that are in order.  
Set  A set is a collection of things, usually numbers.  
Sphere  An object shaped like a round ball  
Subtraction  Taking one number away from another.  
Subtrahend  A quantity or number to be subtracted from another.  
Sum  The result of adding two or more numbers.  
Supplementary angles  The two angles are supplementary angles when they add up to 180°  
Symmetry  When a picture or shape is the same on both sides, we call it ‘symmetrical’  
T  Trapezoid  A trapezoid is a 4sided flat shape with straight sides that has a pair of opposite sides parallel  
Triangle  A triangle has three sides and three angles right arrow. The three angles always add to 180°  
U  Unequal  Not equal.  
V  Vertex  A point where two or more line segments meet. A corner.  
Volume  The volume is the amount of space an object occupies, especially 3D shapes.  For example, the volume is 10 × 4 × 5 = 200 unit  
W  Weight  How heavy something is.  
Whole number  Whole numbers are simply the numbers 0, 1, 2, 3, 4, 5, … (no negative, fractional or decimal parts)  
Word problems  Mathematical exercises presented in ordinary language rather than in mathematical notation. The most common types of word problems are distance problems, age problems, work problems, percentage problems, mixtures problems, and numbers problems.  For example,
Ann is three times as old as her little brother Bob. In five years, she will be only twice as old. How old are they now? 
>>> Parents can also download our free printable set of Math flashcards, and read the detailed guidance of how to use them with your child here: https://blog.e2.com.vn/useflashcardstoteachyourkidsmathvocab/
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