If the fourth power of a number x is equal to a, that is, 4 x multiplied consecutively equals a, then this number x is called the fourth root of a.

Any number has only four fourth roots. Properties of fourth roots: (1) Any number that is not 0 has 4 fourth roots. (2) The fourth root of 0 is 0. In general, if the fourth root of a number X is equal to a, then this number X is called the fourth root of a. In other words, if x⁴=a, then x is called the cube root of a. 0 is the fourth root of 0.