Square root symbol (√)
The square root symbol (√) means the positive number that, multiplied by itself, gives the number under the sign. √100 = 10, read “the square root of 100 is 10”.
How to read it
OpenStax’s Prealgebra calls √ the radical sign and the number under it the radicand, and reads √m as “the square root of m”. Every positive number has two square roots, such as 10 and −10 for 100; the sign stands for the positive one, the principal square root, and −√100 = −10 is written for the other. The code point is U+221A, which Unicode names SQUARE ROOT, with the alias radical sign.
Also searched as: √, radical sign, root symbol.
Look-alikes
Unicode cross-refers √ and the check mark ✓ (U+2713) both ways. In printed maths the root sign normally carries the vinculum over the number; a tick has none. Cube and fourth roots have their own characters, ∛ (U+221B) and ∜ (U+221C).
More math symbols
Browse symbols drawn with lines.
Sources
- Mathematical Operators: Range 2200–22FF (code chart), The Unicode Standard, Version 18.0, Unicode Consortium, Mathematical Operators, 221A–221C
- Dingbats, Range: 2700–27BF (code chart), The Unicode Standard, Unicode Consortium, Dingbats, 2713
- Prealgebra 2e, 5.7 Simplify and Use Square Roots, OpenStax (Rice University), Use Square Root Notation
- Earliest Uses of Symbols of Operation, Jeff Miller, Earliest Uses of Various Mathematical Symbols, MacTutor History of Mathematics, University of St Andrews, Square root
- A History of Mathematical Notations, Vol. I: Notations in Elementary Mathematics, Florian Cajori (Chicago: Open Court, 1928); full text of the Wellcome Collection copy, Internet Archive, § 324, pp. 366–367
Last reviewed September 30, 2026 by Rory Hansen. How we research