## Wikipedia - Electromeric effect (en) Wikipedia - Mesomerer Effekt (de) Wikipedia - Mesomeric effect (en) Wikipedia - Risonanza (chimica) (it) Wikipedia - Мезомерний ефект (uk) Wikipedia - اثر مزومری (fa) Wikipedia - تأثير ميزوميري (ar) mesomeric effect

Also contains definition of: resonance effect
https://doi.org/10.1351/goldbook.M03844
The effect (on reaction rates, @[email protected] equilibria, etc.) attributed to a substituent due to overlap of its p- or π-orbitals with the p- or π-orbitals of the rest of the @[email protected] @[email protected] is thereby introduced or extended, and electronic charge may flow to or from the substituent. The effect is symbolized by M. Strictly understood, the mesomeric effect operates in the ground @[email protected] of the molecule. When the molecule undergoes electronic excitation or its energy is increased on the way to the @[email protected] of a @[email protected], the mesomeric effect may be enhanced by the @[email protected], but this term is not much used, and the mesomeric and electromeric effects tend to be subsumed in the term resonance effect of a @[email protected]