A geometric isomer is a type of isomer that occurs due to the restricted rotation around a double bond or a ring structure in a molecule. This restriction leads to different spatial arrangements of atoms or groups, resulting in distinct compounds with unique properties. The two main types of geometric isomers are cis and trans isomers, which differ in the positioning of substituents relative to the double bond or ring. In cis isomers, similar groups are on the same side, while in trans isomers, they are on opposite sides. Geometric isomerism is important in various fields, including organic chemistry and pharmaceuticals, as these isomers can exhibit different biological activities and chemical reactivities.