square root 
noun
A number which produces a specified quantity when multiplied by itself.The eleven chapters of Halifax's text dealt with topics such as addition, subtraction, multiplication, division, square roots and cube roots....
- Having taken then the square root of this which is 8, subtract from it half the roots, 5 leaving 3.
- The square root of 2 is an irrational number because it can't be written as a ratio of two integers.