f any number, is the fourth power or squared square of that number. Thus 16 is the biquadratic power of 2; for $2 \times 2 = 4$, and $4 \times 4 = 16$.

**Biquadratic Root** of any number is the square root of the square root of that number. Thus the biquadratic root of 81 is 3; for the square root of 81 is 9, and the square root of 9 is 3.