Fourth Root

The Fourth Root at U+221C gives a compact sign for the operation of finding a value whose fourth power equals the expression that follows. It belongs to the Mathematical Operators block and is read as “fourth root of,” as in ∜16 = 2. Its clearest use is in mathematics education, algebra, and technical documents where a short fourth-root expression needs to fit into plain text. In notation, ∜x represents a number y such that y⁴ = x; over the real numbers, ∜81 is 3 and ∜0 is 0, while negative radicands require complex-number interpretation. The symbol also appears in science and engineering when formulas involve inverse fourth-power relationships or quantities derived from fourth powers, such as some scaling laws, statistical moments, or root-mean-fourth calculations. In fully typeset mathematics, many authors instead use a radical sign with a small 4 index, especially for longer expressions, because it gives better visual control over the radicand. A practical point is that this character is specifically the fourth-root operator, not a generic radical. For fifth roots and beyond, indexed radical notation is normally clearer and more widely recognized than looking for a separate single Unicode symbol.