"Vinyl" is a term commonly used in organic chemistry to describe a monosubstituted alkene, and to describe the polyalkane plastics derived from polymerization of monosubstituted ethylene (vinyl) monomers. It is not used in systematic organic nomenclature. The etymological origin of vinyl is uncertain, but it quite likely derived from the nineteenth century term for ethylene (ethene), "weingas" (vinegas, a reference to the role of ethene as a plant hormone). At one time the term vinyl referred primarily to a substituted ethylene, but vinyl now is used frequently to describe any substituted alkene. The use of vinyl is exemplified by the molecule vinyl chloride (its proper systematic name is chloroethylene), CH₂=CHCl. The CH₂=CH- segment is the vinyl functional group, covalently substituted by a chloro group (not ionically bonded to a chloride anion, as the non-systematic name "vinyl chloride" might be taken to imply). Among the other commonly encountered vinyl compounds are vinyl bromide, vinyl ester, vinyl acetate, and vinylbenzene (also called styrene).

Many of these vinyl compounds are made by the reaction of acetylene with electrophiles. For example, HCl adds to acetylene (under pressure at 475K; and in the presence of HgCl₂ as a catalyst) to give vinyl chloride. Vinyl ethers are made by addition of alcohols to acetylene. In contrast, vinyl acetate is made by the metal-catalyzed oxidative acetylation of ethylene by acetic acid, in the presence of O₂ as the oxidant. Radical polymerization of vinyl chloride creates the plastic poly(vinyl chloride), where the vinyl chloride monomers are interconnected (with loss of the alkene double bond) forming the chloro-substituted polyalkane polymer (Figure 1). The vinyl polymers include poly(vinyl chloride) or PVC, poly(vinyl acetate), poly(vinylidene chloride), poly(vinyl alcohol), poly(vinyl acetal), poly(vinyl fluoride), poly(vinyl pyrrolidine, poly(vinyl carbazole), and poly(vinyl ether). Many of these are used as thermoplastics that are shaped and processed by means of injection molding and extrusion.