Maths is complicated, but a good first step on the road to understanding it is to get to know the most useful terms. There are lists in the front of the Bond books, but here’s my own contribution. I hope it helps!

**Algebra**: expressions using letters to represent unknown values, eg 2(x + 3) = 16.

**Angles**: there are three types of angle, depending on the number of degrees.

- acute angles are between 0 and 90 degrees.
- obtuse angles are between 90 and 180 degrees.
- reflex angles are between 180 and 360 degrees.

**Arc**: part of the circumference of a circle.

**Averages**: there are three types of average, and they are all useful in different ways.

- The
**mean**is found by adding up all the values and dividing the total by how many there are, eg the mean of the numbers 1-10 is 5.5, as 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 55, and 55 ÷ 10 = 5.5. - The
**mode**is the most common value (or values), eg the mode of 1, 2, 2, 3, 4, 5 is 2. - The
**median**of an odd number of values sorted by size is the one in the middle, eg the median of the numbers 1-5 is 3. The median of an even number of values is the mean of the two numbers in the middle, eg the median of the numbers 1-10 is 5.5, as 5 and 6 are the numbers in the middle, and 11 ÷ 2 = 5.5.

**Chord**: a straight line drawn between two points on the circumference of a circle.

**Circumference**: the distance all the way round the edge of a circle.

**Congruent**: triangles are congruent if they are the same shape and size, eg two right-angled triangles with sides of 3cm, 4cm and 5cm would be ‘congruent’, even if one is the mirror image of the other. You can prove that two triangles are congruent by using any of the following methods: SAS (Side-Angle-Side), SSS (Side-Side-Side), ASA (Angle-Side-Angle), AAS (Angle-Angle-Side) and RHS or HL (Right-angle-Hypotenuse-Side or Hypotenuse-Leg). If all three measurements of the angles and/or sides are equal, the triangles are congruent. You can only create a congruent copy of a triangle by translation, reflection or rotation. (Note: *congruence* is the same as *similarity*, except that the triangles have to be the same size.)

**Cuboid**: a solid with a rectangle for each of the six sides, eg a shoe box.

**Denominator**: the number on the bottom of a fraction, eg 2 is the denominator of ½.

**Diameter**: the length of a line drawn across a circle passing through the centre.

**Equation**: any line of numbers and operators with an equals sign in the middle, showing that the two sides balance, eg 4x + 12 = 34.

**Factor**: a number that goes into another number evenly, eg 6 is a factor or 12.

**Fibonacci series**: a sequence of numbers created by adding the previous two numbers together to get the next one, eg 1, 1, 2, 3, 5, 8, 13…

**Formula**: a way of calculating the answer to a common problem using letters or words, eg the formula for distance is speed x time (or D = S x T).

**Highest common factor** (or **HCF**): the highest number that goes into two other numbers evenly, eg the HCF of 12 and 18 is 6.

**Improper fraction**: a fraction that is greater than one (in other words, the numerator is greater than the denominator), eg 9/5.

**Lowest common multiple** (or **LCM**) / Lowest common denominator (or LCD): the lowest number that is divisible by two other numbers, eg the LCM of 6 and 8 is 24.

**Multiple**: a number that can be divided evenly by another number, eg 12 is a multiple of 6.

**Numerator**: the number on the top of a fraction, eg 3 is the numerator of ¾.

**Order of operations**: the sequence of doing basic mathematical sums when you have a mixture of, say, addition and multiplication. **BIDMAS** (or **BODMAS**) is a good way of remembering it, as it stands for:

- Brackets
- Indices/Order (in other words, squares, cubes and so on)
- Division and Multiplication
- Addition and Subtraction

Note that division doesn’t come ‘before’ multiplication, and addition doesn’t come ‘before’ subtraction – these operations have to be done in the order in which you find them. For division and multiplication, it doesn’t really matter as it doesn’t change the answer, eg 5 x 8 ÷ 2 = 20, whether you do 5 x 8 first or 8 ÷ 2. However, it *does* matter with addition and subtraction, eg 4 – 3 + 2 = 3 if you do the operations in order, which is correct, but you’d get the wrong answer of -1 if you did 3 + 2 first.

**Operator**: the sign telling you which mathematical operation to do. The most common ones are +, -, x and ÷.

**Parallel**: two lines are parallel if they will never meet, eg the rails on a railway line.

**Perimeter**: the distance all the way round the outside of a shape.

**Perpendicular**: at 90 degrees to each other.

**Pi** (or **π**): a constant used to work out the circumference and area of circles, often shown as 22/7 or 3.14 although it’s actually an ‘irrational’ number, which means it goes on for ever.

**Prime factors**: the lowest prime numbers that can be multiplied together to make a given number, eg the prime factors of 12 are 2² x 3.

**Prime numbers**: a number that can only be divided by itself and one, eg 2, 3, 5, 7, 11, 13…

**Product**: the result of multiplying two numbers together, eg 35 is the product of 5 and 7.

**Quadrilateral**: a four-sided shape such as the following:

**Kite**: a quadrilateral with two pairs of equal sides next to each other (or ‘adjacent’ to each other).**Parallelogram**: a quadrilateral with opposite sides parallel to each other.**Rectangle**: a quadrilateral with two opposite pairs of equal sides and four right angles.**Rhombus**: a quadrilateral with equal sides.**Square**: a quadrilateral with equal sides and four right angles.**Trapezium**: a quadrilateral with one pair of parallel sides. (Note: an isosceles trapezium is symmetrical.)

**Radius**: the distance from the centre of a circle to the circumference.

**Range**: the highest minus the lowest value in a list, eg the range of the numbers 1-10 is 9.

**Regular**: a shape is regular if all its sides and angles are equal, eg a 50p piece is a regular (-ish!) heptagon.

**Right angle**: an angle of 90 degrees.

**Sector**: a ‘slice’ of a circle in between two radii.

**Segment**: a part of a circle separated from the rest by a chord.

**Shapes**: the name of each shape depends on the number of sides. Here are the first 12.

**Quadrilaterals**have four sides.**Pentagons**have five sides.**Hexagons**have six sides.**Heptagons**have seven sides.**Octagons**have eight sides.**Nonagons**have nine sides.**Decagons**have 10 sides.**Hendecagons**have 11 sides.**Dodecagons**have 12 sides.

**Similar**: triangles are similar if they are the same shape, but not necessarily the same size, eg a right-angled triangle with sides of 3cm, 4cm and 5cm is ‘similar’ to a right-angled triangle with sides of 6cm, 8cm and 10cm. (Note: *similarity* is the same as *congruence*, except that the triangles don’t have to be the same size.)

**Square number**: the result of multiplying any number by itself, eg 49 is a square number, as 7 x 7 = 49.

**Square root**: the number that has to be multiplied by itself to make another number, eg 6 is the square root of 36, as 6 x 6 = 36.

**Sum**: the result of adding two numbers together, eg 17 is the sum of 8 and 9.

**Tangent**: either a straight line that touches the circumference of a circle *OR* the length of the opposite side of a triangle divided by the length of the adjacent side

**Triangles**: there are four main types, each with different properties.

- equilateral triangles have all three sides the same length and all three angles the same.
- isosceles triangles have two sides the same length and two angles the same.
- scalene triangles have three sides of different lengths with three different angles.
- right-angled triangles have one 90-degree angle.

**Variable**: an unknown in algebra, eg x or y.