Math & Statistics

What Is a Square Root?

The square root of a number is a value that, when multiplied by itself, gives that number. The square root of 49 is 7, because 7 × 7 = 49. Every positive number has two square roots, one positive and one negative; the symbol √ refers to the positive (principal) root.

Perfect Squares

Numbers such as 1, 4, 9, 16, and 25 have whole-number square roots; others, such as √2 ≈ 1.414, are irrational.

Where It Appears

Standard deviation is the square root of variance, and the side of a square room is the square root of its area.

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🔗 Related Terms

Exponent Standard Deviation Variance Absolute Value

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Last updated: September 29, 2026. This definition is for general educational purposes only. It is not financial, investment, tax, legal, or medical advice, and it does not recommend any product or course of action. For decisions about your own situation, consult a qualified professional.