What √ means, where it came from, and how to type it — click to copy.
Click to copy · U+221A
| Property | Value |
|---|---|
| Character | √ |
| Unicode code point | U+221A |
| Unicode name | SQUARE ROOT |
| Unicode block | Mathematical Operators |
| Category | Math symbol |
| Related precomposed roots | ∛ Cube Root (U+221B), ∜ Fourth Root (U+221C) |
The radical sign traces back to German algebra manuscripts of the 1400s, where mathematicians used a stylized dot or a shorthand letter "r" — short for the Latin radix, meaning root — to mark a root operation. The symbol close to the modern √ first appears in print in Christoff Rudolff's 1525 algebra textbook Coss, one of the earliest printed works on algebra in German.
The horizontal bar that extends over the number or expression being rooted (called the vinculum) was a later refinement, added to make clear exactly what the root applied to — useful once mathematicians started taking roots of entire expressions like √(a + b) rather than single numbers. By the 17th century the combined symbol had become the standard notation across European mathematics, and it hasn't changed meaningfully since.
| Platform | Works? |
|---|---|
| Instagram bio / caption | Yes |
| Discord | Yes |
| TikTok display name | Yes |
| Yes | |
| Roblox username | No — letters, numbers, underscore only |
| PlayStation Network / Xbox Live gamertag | No — alphanumeric only |
| Method | Input |
|---|---|
| Windows Alt code | Alt+251 |
| Mac | Option+V |
| HTML entity | √ or √ |
| CSS content | content: "\221A" |
| LaTeX (standalone glyph) | \surd |
| LaTeX (full expression) | \sqrt{x} |
√ is one of dozens of operators, Greek letters, and set-theory symbols in the full math symbols library.
Browse Math Symbols →On Windows, hold Alt and type 251 on the numeric keypad (Alt+251). On Mac, press Option+V. In HTML, use the entity √ or √.
√x asks "what number, multiplied by itself, gives x?" For example, √9 = 3 because 3 × 3 = 9. The horizontal bar (vinculum) extends over everything being rooted.
No. They look similar at a glance but are different Unicode characters — √ (U+221A, Square Root) is a math operator, while ✓ (U+2713, Check Mark) is a completion/approval mark.
It works in most bios, display names, and chat apps (Instagram, Discord, WhatsApp), but most game platforms — Roblox, PlayStation Network, and Xbox Live — restrict usernames to plain letters, numbers, and a few punctuation marks, so √ will usually be rejected there.