Grignard reagent in the context of "Grignard reaction"

The Grignard reaction (French: [ɡʁiɲaʁ]) is an organometallic chemical reaction in which, according to the classical definition, carbon alkyl, allyl, vinyl, or aryl magnesium halides (Grignard reagent) are added to the carbonyl groups of either an aldehyde or ketone under anhydrous conditions. This reaction is important for the formation of carbon–carbon bonds.