Geometric isomerism, also known as cis-trans isomerism or E-Z isomerism, is a type of stereoisomerism that occurs in compounds with restricted rotation around a double bond or in cyclic compounds. Geometric isomers have the same connectivity of atoms but differ in the arrangement of substituents around the double bond or within a ring. This difference in arrangement can lead to distinct physical properties and chemical behavior.

Here are some key points about geometric isomerism:

1. Double Bond Configuration: Geometric isomerism arises when there is a double bond between two carbon atoms. The orientation of substituents around the double bond determines the isomeric forms.
2. Cis-Trans Nomenclature: In cis isomers, similar substituents are on the same side of the double bond, while in trans isomers, they are on opposite sides.
3. Steric Effects: Geometric isomerism can lead to steric interactions between substituents on adjacent atoms. Cis isomers often have higher steric hindrance than trans isomers.
4. Cyclic Compounds: Geometric isomerism can also occur in cyclic compounds where substituents are positioned differently on a ring.
5. Physical Properties: Geometric isomers can have different physical properties such as melting points, boiling points, and solubility due to their distinct three-dimensional structures.
6. Chemical Reactivity: Geometric isomers can exhibit different chemical reactivity, including different rates of reaction or stereoselectivity in reactions involving the double bond.
7. Optical Isomerism: Geometric isomers are not chiral, and they do not exhibit optical activity. Enantiomers, which arise from chiral centers, are the stereoisomers that exhibit optical activity.
8. Cis-Trans Isomers in Alkenes: One common example of cis-trans isomerism is in alkenes. For example, cis-2-butene and trans-2-butene have different spatial arrangements around the C=C double bond.
9. E-Z System: The E-Z system is an IUPAC-approved method for designating geometric isomers based on the priority of substituents around the double bond.
10. Implications: Geometric isomerism can influence the behavior of molecules in biological systems, materials science, and organic synthesis.

Understanding geometric isomerism is essential for understanding the behavior of molecules with double bonds and cyclic structures. It plays a role in the physical and chemical properties of compounds and has applications in various scientific fields.