In the real number system, the hierarchy of number sets can be organized as follows, from the most specific to the most general:
- Natural Numbers (ℕ): {1, 2, 3, ...} (sometimes including 0: {0, 1, 2, 3, ...})
- Whole Numbers: {0, 1, 2, 3, ...} (sometimes used interchangeably with natural numbers depending on context)
- Integers (ℤ): {..., -3, -2, -1, 0, 1, 2, 3, ...}
- Rational Numbers (ℚ): Numbers that can be expressed as a fraction a/b where a and b are integers and b ≠ 0 (e.g., 1/2, -3, 0.75)
- Irrational Numbers: Numbers that cannot be expressed as a simple fraction (e.g., √2, π, e)
- Real Numbers (ℝ): All rational and irrational numbers combined
So, an accurate hierarchy of number sets within the real number system would be:
Natural Numbers ⊆ Whole Numbers ⊆ Integers ⊆ Rational Numbers ⊆ Real Numbers
(Note: The "Irrational Numbers" are not a separate set within this hierarchy; they are part of the Real Numbers and are a subset of the Rational Numbers' complement.)