The expression "exponent 3 square root 5" can be interpreted as \( (5^{\frac{1}{2}})^3 \).
Using the rule of exponents that states \((a^m)^n = a^{m \cdot n}\), we can rewrite this as:
\[ (5^{\frac{1}{2}})^3 = 5^{\frac{1}{2} \cdot 3} = 5^{\frac{3}{2}} \]
So the expression in terms of rational exponents is:
\[ 5^{\frac{3}{2}} \]
Thus, the rational exponent in fraction form is \(\frac{3}{2}\).