cube root

A cube root of a number is a value that, when cubed (multiplied by itself three times), gives that number. It undoes cubing. Since 2 × 2 × 2 = 8, the cube root of 8 is 2, written cbrt(8) = 2 or with a small index 3 on the radical.

Unlike square roots, the cube root behaves nicely with negative numbers: a negative times a negative times a negative is negative, so cbrt(−8) = −2. Every real number — positive, negative, or zero — has exactly one real cube root, and it keeps the same sign as the original number.

Geometrically, if a cube has volume V, its edge length is cbrt(V). Many cube roots are irrational, such as cbrt(2) ≈ 1.2599…, and are left in radical form unless a decimal estimate is needed.