Cycloalkanes:

Substituted cycloalkanes can also present like a configurational isomers. For instance, there are 2 configurational isomers of 1, 2-dimethylcyclopropane depending upon whether the methyl groups are on similar side of the ring or on opposite (reverse) sides. The relative positions of the methyl groups can be described through the bonds. A solid wedge points out that the methyl group is emerging the page towards you, while a hatched wedge points out that the methyl group is pointing into the page away from you. If the substituents are on similar side of the ring, the structure is described as cis. If they are on opposite (not similar) sides, the structure is termed as trans.

Figure   (a) cis-1, 2-Dimethylcyclopropane; (b) trans-1, 2-dimethylcyclopropane.