<P> Cis -- trans isomerism , also known as geometric isomerism or configurational isomerism , is a term used in organic chemistry . The prefixes `` cis '' and `` trans '' are from Latin . In the context of chemistry , cis indicates that the functional groups are on the same side of the carbon chain while trans conveys that functional groups are on opposing sides of the carbon chain . Cis - trans isomers are stereoisomers , that is , pairs of molecules which have the same formula but whose functional groups are rotated into a different orientation in three - dimensional space . It is not to be confused with E -- Z isomerism , which is an absolute stereochemical description , and only to be used with alkenes . In general , stereoisomers contain double bonds that can not rotate , or they may contain ring structures , where the rotation of bonds is restricted or prevented . Cis and trans isomers occur both in organic molecules and in inorganic coordination complexes . Cis and trans descriptors are not used for cases of conformational isomerism where the two geometric forms easily interconvert , such as most open - chain single - bonded structures ; instead , the terms `` syn '' and `` anti '' would be used . </P>
what is the difference between cis and trans molecules
same side of the carbon chain opposing sides of the carbon chain