Square root sign

A hooked stroke with a horizontal bar, indicating a root of a number.

Also known as: Radical sign, Root symbol, Surd

MathematicalScientificKeyboard & punctuationStandard profile

Meanings

The radical sign indicates a square root, or with an index, a higher root. The overbar shows exactly how much of the expression the root applies to.

Common modern usageVerified fact
Indicates the square root of the quantity beneath it — the number which, multiplied by itself, gives that quantity.
Contexts: Mathematics
Common modern usageVerified fact
Carries a small index to indicate higher roots, so a raised 3 denotes a cube root.
Contexts: Mathematics
Common modern usageVerified fact
Uses its horizontal overbar, the vinculum, to mark exactly which terms fall under the root — a grouping device as much as a symbol.
Contexts: Mathematics

A short rising stroke turning into a tall hooked stroke with a bar extending right.

IdentityHigh confidence: High confidence because the identity is defined by a current official standard.
Historical originLow confidence: Low confidence because the historical origin is documented in encyclopedic references, but only a single source has been found so far, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Visual matchHigh confidence: High confidence because the visual match is defined by a current official standard.

Square root
Wikipedia · retrieved 2026-07-30
Tertiary reference. Used for widely-agreed identity and origin summary, not for contested detail or exact dates.
Unicode Code Chart: Mathematical Operators (U+2200–U+22FF)
The Unicode Consortium · retrieved 2026-07-30
Authoritative for the character's code point, name and block only. Unicode assigns identity; it does not define what a symbol means in use.

Last reviewed 2026-07-30

Meanings

The radical sign indicates a square root, or with an index, a higher root. The overbar shows exactly how much of the expression the root applies to.

Common modern usageVerified fact

Indicates the square root of the quantity beneath it — the number which, multiplied by itself, gives that quantity.

Common modern usageVerified fact

Carries a small index to indicate higher roots, so a raised 3 denotes a cube root.

Common modern usageVerified fact

Uses its horizontal overbar, the vinculum, to mark exactly which terms fall under the root — a grouping device as much as a symbol.

Confidence

IdentityHigh confidence: High confidence because the identity is defined by a current official standard.
Historical originLow confidence: Low confidence because the historical origin is documented in encyclopedic references, but only a single source has been found so far, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Visual matchHigh confidence: High confidence because the visual match is defined by a current official standard.

Sources

Square root
Wikipedia · retrieved 2026-07-30
Tertiary reference. Used for widely-agreed identity and origin summary, not for contested detail or exact dates.
Unicode Code Chart: Mathematical Operators (U+2200–U+22FF)
The Unicode Consortium · retrieved 2026-07-30
Authoritative for the character's code point, name and block only. Unicode assigns identity; it does not define what a symbol means in use.

Last reviewed 2026-07-30