Example: \(\ce{p-XC6H4Y}\), where an electron pair can be delocalized from electron-donating \(\ce{X}\) not only to ring carbons but also to electron-withdrawing \(\ce{Y}\).

Note 1: This may be contrasted with cross-conjugation.

Note 2: In Hammett-type correlations (linear Gibbs-energy relationships), this situation can lead to exalted substituent constants \(\sigma^{+}\) or \(\sigma^{-}\), as in solvolysis of \(\ce{p-CH3OC6H4C(CH3)2Cl}\) or acidity of \(\ce{p-nitrophenol}\), respectively.