- Counting Numbers \(\N\)
- sometimes include 0, sometimes don’t

- Integers \(\Z\) : {…,-5,-4,-3,-2,-1,0,1,2,3,4,5,…}
- Whole number = number without fractional part

- Rational numbers: \(ℚ\)
- can be represented as a quotient of two integers, excluding 0 for the denominator

- Irrational numbers: \(\mathbb I = \{x \mid x\in \mathbb R \land x \notin \mathbb Q\}\)
- Real: \(\R\)
- Complex: \(\mathbb C\)