Plain-language meanings for 53 words that come up in GCSE Maths, in alphabetical order. They are written to help you understand the idea, so check your exam board’s specification if you need an exact wording.
A
- Alternate angles
- Equal angles on opposite sides of a line that crosses two parallel lines. They sit between the parallel lines and form a Z shape. See also: Parallel.
- Area
- How much flat surface a 2D shape covers, measured in square units such as cm². A rectangle has area length × width. See also: Perimeter, Volume.
B
- Bearing
- A direction given as an angle measured clockwise from north, written with three figures. East is 090° and south-west is 225°.
C
- Circumference
- Distance around the edge of a circle. It equals π × diameter. See also: Diameter.
- Coefficient
- Number multiplying a letter in a term. In 7x the coefficient is 7. See also: Term, Variable.
- Compound interest
- Interest worked out on the original amount plus any interest already added. £100 at 3% a year for two years becomes 100 × 1.03² = £106.09. See also: Percentage change.
- Congruent
- Exactly the same shape and the same size. One shape can be turned, slid or flipped to fit exactly on top of the other. See also: Similar shapes.
D
- Denominator
- Bottom number of a fraction. It tells you how many equal parts the whole is split into. See also: Numerator.
- Density
- How much mass there is in each unit of volume: density = mass ÷ volume. It is often measured in g/cm³. See also: Volume.
- Diameter
- A straight line across a circle that passes through the centre. It is twice the radius. See also: Circumference, Tangent.
- Direct proportion
- A link between two quantities where they grow at the same rate, so doubling one doubles the other. Their ratio stays the same. See also: Inverse proportion, Ratio.
E
- Equation
- A statement that two expressions are equal, with an equals sign, such as 3x + 2 = 11. You can solve it to find the unknown value. See also: Expression, Identity.
- Expand
- Multiply out brackets. For example, 3(x + 2) expands to 3x + 6. See also: Factorise.
- Expression
- A group of terms joined by plus or minus signs with no equals sign, such as 3x + 2. You can simplify it but not solve it. See also: Equation, Term.
F
- Factor
- A whole number that divides exactly into another with no remainder. Factors of 12 are 1, 2, 3, 4, 6 and 12. See also: Multiple, Prime number.
- Factorise
- Write an expression as a product by taking out a common factor. For example, 6x + 9 factorises to 3(2x + 3). See also: Expand, Quadratic.
- Formula
- A rule written in letters that links quantities, such as A = lw for the area of a rectangle. See also: Subject.
- Frequency
- Number of times a value, or a value in a group, occurs in a set of data. See also: Mean.
G
- Gradient
- How steep a line is. It equals the change upwards divided by the change across, so a line rising 6 over a run of 2 has gradient 3.
H
- Hypotenuse
- Longest side of a right-angled triangle. It is opposite the right angle.
I
- Identity
- An equation that is true for every value of the letter, written with the ≡ sign. For example, 2(x + 1) ≡ 2x + 2. See also: Equation.
- Independent events
- Events where one outcome has no effect on the chance of the other, such as flipping a coin and then rolling a dice. Multiply the two probabilities to find the chance of both. See also: Mutually exclusive events, Probability.
- Inequality
- A statement comparing values using <, >, ≤ or ≥. For example, x > 3 means x is any number bigger than 3.
- Integer
- A whole number, which can be positive, negative or zero. 5, 0 and −12 are integers; 2.5 is not.
- Inverse proportion
- A link between two quantities where one goes up as the other goes down, so that their product stays the same. If a job takes 4 workers 6 hours, 8 workers at the same pace take 3 hours. See also: Direct proportion.
- Irrational number
- A number that cannot be written as a fraction of two integers. Its decimal goes on forever without repeating. π and √2 are examples. See also: Surd.
M
- Mean
- Average found by adding all the values and dividing by how many there are. For 2, 4 and 9 the mean is 15 ÷ 3 = 5. See also: Median, Mode, Range.
- Median
- Middle value when the data is in order. With an even number of values, it is halfway between the two middle ones. See also: Mean, Mode.
- Mode
- Value that occurs most often. A set of data can have more than one mode. See also: Mean, Median.
- Multiple
- A number you get by multiplying a whole number by another whole number. Multiples of 5 include 5, 10, 15 and 20. See also: Factor.
- Mutually exclusive events
- Events that cannot both happen at the same time, such as rolling a 2 and rolling a 5 on a single throw. Their probabilities can be added to find the chance of either. See also: Independent events, Probability.
N
- Numerator
- Top number of a fraction. It tells you how many of the equal parts you have. See also: Denominator.
P
- Parallel
- Lines that stay the same distance apart and never meet. Arrows on a diagram show lines that are parallel. See also: Perpendicular, Alternate angles.
- Percentage change
- How much a value has changed, shown as a percentage of the original: change ÷ original × 100. Going from 80 to 92 is a 15% increase. See also: Compound interest.
- Perimeter
- Total distance around the outside of a 2D shape. See also: Area.
- Perpendicular
- At right angles (90°) to each other. See also: Parallel.
- Prime number
- A whole number greater than 1 with exactly two factors: 1 and itself. 2, 3, 5 and 7 are prime; 1 is not. See also: Factor.
- Probability
- A number from 0 to 1 that says how likely an event is. 0 means it cannot happen and 1 means it is certain. It can be given as a fraction, decimal or percentage. See also: Independent events.
- Product
- Answer when numbers or terms are multiplied. For 4 and 6 the product is 24. See also: Factorise.
Q
- Quadratic
- An expression or equation where the highest power of the letter is 2, such as x² + 5x + 6. Its graph is a curve called a parabola. See also: Factorise.
R
- Range
- Difference between the largest and smallest values. It is a simple measure of how spread out the data is. See also: Mean.
- Ratio
- A way of comparing the sizes of quantities. Mixing 2 parts blue paint with 3 parts white gives the ratio 2 : 3. See also: Direct proportion.
- Reciprocal
- Number that multiplies with a given number to make 1. Reciprocal of 4 is 1/4, and of 2/3 is 3/2. Zero has no reciprocal.
S
- Sequence
- A list of numbers that follows a rule, such as 3, 7, 11, 15 where each term is 4 more than the one before. See also: Term.
- Similar shapes
- Shapes that are the same shape but not necessarily the same size. Matching angles are equal and matching lengths are in the same ratio, called the scale factor. See also: Congruent, Ratio.
- Simplify
- Write something in a neater form, for example by collecting like terms or cancelling a fraction. 3x + 2x simplifies to 5x. See also: Expression.
- Standard form
- A way to write very large or very small numbers as A × 10n, where A is at least 1 but less than 10 and n is an integer. For example, 0.00045 = 4.5 × 10−4. See also: Integer.
- Subject
- Letter on its own on one side of a formula. In v = u + at, the subject is v. See also: Formula.
- Surd
- An irrational root, such as √3, left as a root rather than written as a decimal. Leaving it as a surd gives an exact answer. See also: Irrational number.
T
- Tangent
- A straight line that touches a circle at exactly one point. It meets the radius at that point at 90°. See also: Diameter, Perpendicular.
- Term
- One part of an expression, separated from the others by plus or minus signs. In 3x² + 5x − 1 there are three terms. See also: Expression, Coefficient.
V
- Variable
- A letter that stands for a quantity that can take different values. See also: Coefficient.
- Volume
- How much space a 3D solid takes up, measured in cubic units such as cm³. A cuboid has volume length × width × height. See also: Area, Density.
Part of the GCSE Maths revision set: the revision guide, self-marking quiz and comparison of the three exam boards.