Radical Expressions
Each radical expression has an index and a radicand.
The square root is the most popular radical. For instance $\sqrt[2]{9}$ has a radicand of 9 and index of 2. However, it is written as $\sqrt{9}$ and the index of two is understood. "Squaring" a number and "taking the square root" are opposite operations.
${3}^{2}=9\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}so\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\sqrt{9}=3$
Numbers can be raised to powers other than two. For instance numbers can be cubed (raised to the 3^{rd} power), and raised to the 4^{th}, 5^{th} , 6^{th} and so on........ In the same way numbers can have different "roots".
Radical 
Read as 
Example 
Opposite Operation 

Square root 
$\sqrt{25}=5$ 
5^{2} = 25 

Cube root 
$\sqrt[3]{8}=2$ 
2^{3}= 8 

Fourth root 
$\sqrt[4]{81}=3$ 
3^{4} = 81 

nth root 
Used to indicate "any" root 
Radical expression 
Simplified answer 
Perfect/NonPerfect 
$\sqrt{36}$ 
6 because 6^{2} = 36 
Perfect square 
$\sqrt[3]{27}$ 
3 because 3^{3} = 27 
Perfect cube 
$\sqrt{7}$ 
$\sqrt{7}$ answer in radical form 2.6 approximate answer 
NonPerfect 
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