radical sign

WordReference Random House Learner's Dictionary of American English © 2026

ˈrad•i•cal ˌsign, n. [countable] [Math.]

1. Mathematics the symbol √ or √ ̅, indicating that a quantity is a root of the quantity that is shown after or under the symbol, e.g., √25=5.

WordReference Random House Unabridged Dictionary of American English © 2026

rad′ical sign′, [Math.]

1. Mathematics the symbol √ or √ ̅ indicating extraction of a root of the quantity that follows it, as √25=5 or ∛a³b³ = ab.

• 1660–70

Collins Concise English Dictionary © HarperCollins Publishers::

radical sign noun

1. the symbol √ placed before a number or quantity to indicate the extraction of a root, esp a square root. The value of a higher root is indicated by a raised digit in front of the symbol, as in ³√