A rational number is defined as any number that can be expressed as the quotient or fraction \( \frac{a}{b} \), where \( a \) and \( b \) are integers, and \( b \) is not zero.
The number 10 can be expressed as:
\[ \frac{10}{1} \]
Here, both the numerator (10) and the denominator (1) are integers, and the denominator is not zero. Therefore, since 10 can be represented as a fraction in this form, it is classified as a rational number.