A perfect cube is a number that can be expressed as the cube of an integer. Let's analyze the options:
- \( 9 = 3^2 \) (not a perfect cube)
- \( 18 = 2 \times 3^2 \) (not a perfect cube)
- \( 27 = 3^3 \) (perfect cube)
- \( 36 = 6^2 \) (not a perfect cube)
So, the perfect cube from the options given is 27.