What are the necessary conditions for any system to be aromatic?

(N/A) compound is said to be aromatic if it satisfies the following three conditions:
$(i)$ The molecule must be cyclic and planar.
$(ii)$ The $\pi$-electrons of the compound must be completely delocalized within the ring.
$(iii)$ The total number of $\pi$-electrons present in the ring must follow $H$ückel's rule,which is $(4n + 2)$ $\pi$-electrons,where $n$ is an integer $(n = 0, 1, 2, \dots)$.