For all non-negative $\displaystyle \ \ x, \ \ x^{1/2} \ = \ \sqrt{x}.$
$\displaystyle f(x) \ = \ \sqrt{x} $ is a function. As such, it gives one value.
Given the fact that the original post is is the pre-university elementary algebra forum I find the post #14 spot-on and I find those of zzephod off-putting in that they are totally inappropriate for the level of discussion.
Suppose $x\in\mathbb{R}$ then
$\displaystyle \text{square root(s)}(x)=\begin{cases}\text{does not exist } &: x<0 \\ 0 &: x=0\\ \pm\sqrt x&:x>0\end{cases}$