A perfect cube is a number that can be written as the product of three identical integers. In other words, a number is a perfect cube if it is the cube of an integer.

Similarly, if a variable has an exponent that is a multiple of $3,$ it is said that it is a perfect cube. This is because this condition guarantees that the variable can be rewritten as the product of three identical powers with integer exponents. $$\begin{array}{rl}{y}^3& \iff y\times y\times y\\ x^6& \iff x^2\times x^2\times x^2\end{array}$$