Using the Square Root Symbol
The square root symbol, properly called the radical sign, comes from a stylised letter r, the first letter of the Latin radix (root). Christoph Rudolff printed it in 1525, and Descartes later added the horizontal bar, the vinculum, that stretches over the whole expression being rooted. The Unicode character √ carries only the tick; the bar is something a maths renderer draws over the argument, which is why √ pasted into a chat looks slightly unfinished next to a textbook.
How to write a root in plain text
With no vinculum available, use brackets to show how far the root extends: √(a² + b²) rather than √a² + b², which a careful reader will take as (√a)² + b². For a single number or variable, no brackets are needed: √2, √x, 3√5. Higher roots have their own characters, ∛ and ∜, and beyond that you fall back to fractional exponents such as x^(1/5).
In equations and code
Word's equation editor and LaTeX both draw the full radical: \sqrt{x} in LaTeX, and in Word the linear form \sqrt(x) converts when you press space inside an equation. Programming languages skip the symbol entirely and call a function, Math.sqrt(x) in JavaScript, math.sqrt(x) in Python or =SQRT(A1) in Excel. The Unicode glyph belongs in prose, labels, comments and captions, not in a formula cell.
√ as a tick
Because the radical looks like a check mark, it has spent decades doing double duty on paper forms and in plain-text lists. That habit predates Unicode: early character sets on typewriters and 8-bit computers had √ but no ✓, so "√ done" became a convention. Today every phone and browser can show a true tick, and the check mark symbols page has ✓, ✔ and ☑ ready to copy. Screen readers announce √ as "square root", which makes a list of tasks sound odd, so use a proper check when accessibility matters. Gboard still places √ on its symbols page beside π and ÷, which is one reason the habit persists on Android.
Typing it
Mac users get it from Option + V. Windows has no Latin-1 Alt code, but the DOS-era Alt + 251 works in many applications, and Word converts 221A to √ after Alt + X. The iPhone keyboard omits it entirely, so set up a text replacement or paste from this page.
Everyday and creative uses
Beyond homework, √ appears in "√ approved" stamps on fan art, in gaming bios as a stylised tick, and in maths-themed handles alongside the pi symbol and the infinity symbol. Its angular stroke suits monospaced and typewriter fonts, where it sits at the same height as the capitals and reads cleanly even at small sizes.