The tick-and-bar we reach for without thinking started life as a bare check mark. Christoff Rudolff put it into print in his 1525 algebra Die Coss, drawing a symbol like a small r with a long tail and no bar over the number — most likely a stylised r for the Latin radix, "root". A competing legend traces it to the Arabic letter jim, but Rudolff left no explanation. The horizontal bar, the vinculum, that now tells you exactly how much sits under the root came later: Descartes joined it to the sign in 1637, and the modern radical is really those two inventions fused.
That missing bar is still the practical gotcha. Written by hand or in plain text, the root of 2 plus 3 is ambiguous — does the root cover the 3? The vinculum resolves it, which is why typeset math stretches the bar over the whole radicand. For roots other than square you tuck a small index into the crook: the cube root is the same sign with a 3. Reach for the real character rather than a lowercase v or a check mark; screen readers and search both treat it as the operator it is.
About Square Root
Square Root is the Unicode character √ at codepoint U+221A in the Mathematical Operators block of the Basic Multilingual Plane (BMP).
Technical Reference
| Unicode Codepoint | |
| Decimal | |
| UTF-8 (hex) | |
| UTF-16 (hex) | |
| HEX Entity | |
| HTML Entity | |
| CSS (\xxxx) | |
| JavaScript | |
| Python |
How to Use Square Root
To use the Square Root symbol (√) in HTML, insert the
entity √ directly into your markup. The decimal entity √ works in any HTML-serialised document.
In CSS pseudo-elements use content: '\221A';.
In JavaScript and TypeScript the escape '\u221A' evaluates to √. In Python source, write '\u221A'.
The character encodes to E2 88 9A as UTF-8 bytes and 221A as UTF-16 code units. Its decimal codepoint is 8730.
This is a text-based Unicode character. It will render in the current font on most platforms. If a font lacks this glyph, the browser may show a placeholder or fall back to a system font.