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Number systems key terms
Study Number systems with curriculum-aligned Key Terms resources, practice links, and exam-focused support.
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key terms
Resource type
Topic
Number systems
Key terms
Natural number
A number belonging to the set ℕ, which is defined here as {0, 1, 2, 3, …}.
Set
A collection of values considered together; ℕ is the set containing the natural numbers.
Integer
A whole-number value that may be negative, zero, or positive.
ℤ
The symbol used for the set of integers: { …, -3, -2, -1, 0, 1, 2, 3, … }.
Rational number
A number that can be written as a fraction or ratio of integers.
ℚ
The set of rational numbers, including all integers.
Irrational number
A number that cannot be written as a fraction.
Fraction
A way of writing a number using a numerator and denominator, such as 1/2.
Real number
A number belonging to ℝ, the set that includes natural, rational and irrational numbers and represents possible real-world quantities.
Irrational number
A real number that is not rational.
Ordinal number
A number that describes the numerical position of an object in an ordered arrangement.
Well-ordered set
A set whose objects have been placed in a definite order, allowing their positions to be described using ordinal numbers.
Natural number
A number used for counting.
Real number
A number used for measurement, including measurements that may have fractional values.
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