Chapter 5 - Number Theory and the Real Number System - 5.5 Real Numbers and Their Properties; Clock Addition - Exercise Set 5.5 - Page 308: 7

$\frac{2}{3}$ is a rational number that is not a whole number.

WHole numbers start at zero and continue to infinity in whole number increments, for example: 0, 1, 2, 3, 4, 5, ... There are not fractions in the set of whole numbers. The number $\frac{2}{3}$ is not a whole number.