According to Huckel's rule, the molecules which are considered as aromatic, refer to planar cyclically conjugated structures having (4n+2)π-electrons (where n is 0,1 , 2,3... etc.). The alicyclic compounds which do not have (4n+2)π-electrons are called non-aromatic compound. e.g.,
Aromatic molecule containing 6π electron =(4×1+2)π electrons.