Area
The amount of flat space inside a shape, counted in square units.
Topic: Area & perimeter
GCSE Maths key terms A to Z
Plain-English meanings of the words GCSE Maths questions lean on. 45 terms. Where Yumio has a topic page for the idea, the link is beside it.
A
B
Bound
The smallest and biggest values a rounded number could really have been.
Also written: bounds, error interval
Topic: Bounds
C
Coefficient
The number in front of a letter. It tells you how many of that letter you have.
D
Decimal place
The number of digits after the decimal point.
Also written: decimal places, d.p., dp
Denominator
The bottom number of a fraction. It says how many equal parts the whole is cut into.
Difference
How far apart two numbers are: the bigger one take away the smaller one.
E
Equation
Two sides with an equals sign between them. Solving it means finding the value of the letter that makes both sides equal.
Topic: Solving one-step equations
Equivalent fraction
Fractions that look different but are the same amount. You multiply or divide the top and bottom by the same number.
Also written: equivalent fractions, equivalent
Expand
Multiply out the brackets so that every term inside gets multiplied by what is outside.
Topic: Expanding & factorising
Expression
Numbers and letters joined by signs, with no equals sign. You can simplify an expression but you cannot solve it.
Topic: Writing an expression
F
Factor
A factor of a number is a whole number that divides into it exactly, with nothing left over.
Also written: factors
Topic: Factors & multiples
Factorise
Put brackets back in: take out the biggest factor that every term shares.
Also written: factorize
Fraction
A fraction is part of a whole. The bottom number says how many equal parts, the top number says how many you have.
G
Gradient
How steep a line is: how far it goes up for every 1 step across.
Also written: slope
Topic: Gradient of a line
H
Hypotenuse
The longest side of a right-angled triangle. It is always opposite the right angle.
I
Inequality
A comparison that is not equal: one side is bigger or smaller than the other, using <, >, ≤ or ≥.
Integer
A whole number. It can be negative, zero or positive, but never a fraction or decimal.
Intercept
The point where a line crosses an axis. The y-intercept is where it crosses the vertical axis.
Also written: y-intercept
M
Mean
The mean is the usual average: add up all the values, then divide by how many values there are.
Also written: average
Median
The middle value when the numbers are put in order from smallest to biggest.
Mode
The value that appears most often.
Multiple
A multiple of a number is what you get when you multiply it by 1, 2, 3 and so on. It is in that number's times table.
Also written: multiples
Topic: Factors & multiples
N
Nth term
A rule that gives any term in a sequence from its position number, n.
Topic: Sequences (nth term)
Numerator
The top number of a fraction. It says how many parts you have.
P
Percent
Percent means out of 100. 50 percent is half, because 50 is half of 100.
Also written: percentage, per cent
Perimeter
The distance all the way around the outside of a shape.
Topic: Area & perimeter
Power
The small raised number. It tells you how many times to multiply the number by itself.
Also written: index, indices, exponent
Topic: Powers & roots
Prime
A prime number has exactly two factors: 1 and itself. 1 is not prime.
Also written: prime number
Topic: Prime factors, HCF & LCM
Probability
How likely something is, from 0 (impossible) to 1 (certain). It is the number of ways you want divided by the number of ways it could happen.
Topic: Probability
Product
The answer when you multiply numbers together.
Proportion
Two amounts are in proportion when one grows or shrinks at the same rate as the other, so doubling one doubles the other.
Also written: proportional
Topic: Proportion
Q
Quotient
The answer when you divide one number by another.
R
Range
How spread out the values are: the biggest value take away the smallest value.
Ratio
A way to compare amounts. 2 : 3 means for every 2 of one thing there are 3 of the other.
Topic: Writing & simplifying ratio
Reciprocal
The number you multiply by to get 1. You find it by flipping the fraction upside down.
Topic: Cubic and reciprocal graphs
S
Sequence
A list of numbers that follow a rule, in order.
Significant figure
Counting digits from the first one that is not zero.
Also written: significant figures, s.f., sf
Simplify
Make it as small and tidy as you can without changing its value. For a fraction, divide the top and bottom by the biggest number that goes into both.
Also written: simplest form, lowest terms
Square
To square a number, multiply it by itself.
Also written: squared
Topic: Completing the square
Square root
The number that multiplies by itself to give the number you started with.
Also written: root
Standard form
A way to write very big or very small numbers as a number between 1 and 10 times a power of 10.
Topic: Standard form
Sum
The answer when you add numbers together.
T
Term
One part of an expression. Terms are separated by plus and minus signs, and each term keeps the sign in front of it.
Also written: terms
Topic: Sequences (nth term)
V
Variable
A letter that stands for a number we do not know yet, or a number that can change.
Also written: unknown
Volume
The amount of space inside a solid shape, counted in cubic units.
Topic: Volume of a prism
Learn the words that tell you what to do in a question: GCSE Maths command words. Learn the formulae: formula sheet.