The set of numbers that is always irrational is non-terminating, non-repeating decimals.
- Positive decimals can be either rational (like 0.5) or irrational (like √2).
- Terminating decimals (like 0.75) are rational.
- Repeating decimals (like 0.333...) are also rational.
Only non-terminating, non-repeating decimals (like π or e) are classified as irrational numbers.