Simplify. \[ \sqrt{y^{19}} \]

Step 1 ：Rewrite the expression \(\sqrt{y^{19}}\) as \(y^{19/2}\).

Step 2 ：Since 19 is an odd number, we can't simplify it further without knowing the value of y.

Step 3 ：If y is a positive number, we can simplify it to \(y^{9} \cdot \sqrt{y}\).

Step 4 ：If y is a negative number, the result would be complex and can't be simplified further.

Step 5 ：Since the question doesn't specify the value of y, we can't simplify it further.

Step 6 ：Final Answer: \(\boxed{y^{9} \cdot \sqrt{y}}\)