In a system $\ce{XC6H4GY}$ this is conjugation involving the substituent $\ce{X}$, the benzene ring and the side-chain connective-plus-reaction site $\ce{GY}$, i.e. either $\ce{X}$ is a $+R$ group and $\ce{GY}$ is a $-R$ group, or $\ce{X}$ is a $-R$ group and $\ce{GY}$ is a $+R$ group. In Hammett correlations this situation can lead to the need to apply exalted substituent constants \(\sigma ^{+}\) or \(\sigma ^{-}\), respectively, as in electrophilic or nucleophilic aromatic substitution, respectively. The term 'through resonance' is synonymous. Cross conjugation has also been used to describe the interactions occurring in 2-phenylallyl and similar systems.