The correct response is irrational.
Irrational numbers are real numbers that cannot be expressed as a fraction of two integers (i.e., they cannot be written in the form \( \frac{a}{b} \) where \( a \) and \( b \) are integers and \( b \neq 0 \)). Examples of irrational numbers include \( \pi \) and \( \sqrt{2} \).