1,4-Addition reactions of α, β–unsaturated carbonyl compounds and α, β–unsaturated nitriles with resonance-stabilized carbon nucleophiles, such as enolate ions and enamines, are known as Michael addition.  The α, β–unsaturated compounds undergoing Michael addition is called the Michael acceptor, the nucleophile Michael donor, and the product Michael adduct.

eg:

mechanism:

See also Robinson annulation.