• Natural Numbers (ℕ): {1, 2, 3, 4, …}

    • Used for counting.

    • Closed under addition and multiplication.

  • Integers (ℤ): {…, -3, -2, -1, 0, 1, 2, 3, …}

    • Extends natural numbers by including zero and negative numbers.

    • Allows subtraction.

  • Rational Numbers (ℚ): {a/b | a, b are integers, b ≠ 0}

    • Includes fractions and whole numbers.

    • Allows division (except by zero).

  • Irrational Numbers: {√2, π, e, …}

    • Cannot be written as a fraction (a/b form).

    • Decimal representation is non-repeating and non-terminating.

  • Real Numbers (ℝ):

    • Includes both rational and irrational numbers.

    • Represents all points on a number line.