square root

noun2

1. •
   The number which, when squared, yields another number.

   • The square roots of 4 are 2 and −2, the square root of 0 is 0, and the square roots of −4 are 2i and −2i.
2. •
   The positive number which, when squared, yields another number: the principal square root.

   • The square root of 4 is 2. No negative real square roots exist. Negative numbers have no real square roots.