Square root symbol √

• √25 = 5, because 5 × 5 = 25.
• √2 ≈ 1.414 is irrational: its decimals never end or repeat.
• By convention, √ means the principal (nonnegative) root, so √9 is 3, not −3. The equation x² = 9 still has two solutions, x = ±3, which is why the quadratic formula puts ± in front of the root.
• In print, a bar (the vinculum) extends over everything under the root. √(x + 1) is not the same as √x + 1, so in plain text always use parentheses.

Other roots use a small index: ∛8 = 2 (cube root) and ∜16 = 2 (fourth root). Both are single characters you can copy from the look-alike list on this page.

Some fonts make √ look like a check mark, and older documents sometimes used it that way. Avoid it. A screen reader typically announces √ as “square root,” and spreadsheets, filters and search tools won’t treat it as a check. For checklists and “done” columns, use ✓ or ✔ instead.

The reverse happens too: a ✓ pasted into a formula reads as a check mark, not a root. Pick the character that matches the meaning, and your document stays correct when it is searched, read aloud or converted.

• Word: in an equation (Alt+=), type \sqrt and press space to get a root that stretches over its contents. \cbrt gives a cube root.
• Excel and Google Sheets: =SQRT(A1). For other roots, use a power: =A1^(1/3) is the cube root.
• Programming: Math.sqrt(x) in JavaScript, math.sqrt(x) in Python, or x ** 0.5.
• LaTeX: \sqrt{x}, and \sqrt[3]{x} for a cube root.
• Android (Gboard): √ is on the second symbols page.
• iPhone: no default key; copy it here or use a text replacement.