What are the term names of root equation? In exponentiation we have terms:
$$\text{base}^\text{exponent} = \text{power}.$$
But how the terms are called when dealing with the $n$-th root? For example: 
$$\sqrt[n]{x} = z. $$
What are the names of the $n$, $x$, and $z$ terms in this expression?
If there are multiple names, please mention them all if possible.
 A: You can call $x$ either the argument or the radicand (the thing under the radical sign), and $z$ itself is the $n$th root. The value "$n$" does not have a name.
A: Radicand is the quantity under the root sign, and $n$ is the index; the result is a surd.
See this MathWorld page.
A: In the expression $\sqrt[n]{x} = z$:


*

*Generally speaking, the term $z$ is an $n$-th root of $x$.  The expression itself will typically be defined in context such that it has a unique value, e.g. we will write $\sqrt[3]{8} = 2$ (and not, for example, $-1+i\sqrt{3}$, which also cubes to $8$).  The notation might also indicate the principal $n$-th root of $x$.  When $n=2$, we typically simplify the notation and write
$$ \sqrt{x} = z. $$
In this case, $z$ is called the (principal) square root of $x$.  When $x=1$, $z$ is a (principal) root of unity, e.g.
$$ \sqrt[n]{1} = \text{the principal $n$-th root of unity}. $$
Roots of unity play a special role in a branch of math called "complex analysis."  One might also see $z$ referred to as a surd.

*The term $x$ is the radicand.  Alternatively, if we regard $\sqrt[n]{\cdot}$ a a function, we might refer to $x$ as the argument of that function or, perhaps, the argument of the radical expression.

*Most often, the $n$ is called the index of the radical.  It may also be referred to as the degree.  I have not seen this term in the wild, but a quick search of the interwebs indicates that this is not an uncommon terminology.

*As long as we are giving names to things, the symbol $\sqrt{}$ is called the radical or surd, and the horizontal line over the radicand is called a vinculum.  Note that nearly any horizontal bar in mathematics may be called a vinculum (e.g. the horizontal bar in the fraction $\frac{1}{2}$ is also a vinculum).
