- (mathematics) A number which, when squared, yields another number.
- The square roots of 4 are 2 and -2, the square root of 0 is 0, and -5 has no square root.
- (mathematics) A positive number which, when squared, yields another number.
- The square root of 4 is 2. No negative square roots exist.
Even in mathematical contexts, square root generally means positive square root. If there is a chance of ambiguity, prefer constructions like a square root or a complex square root to indicate the first definition, or the positive square root or similar to indicate the second sense.