Stereospecific polymerization is a polymerization in which the mechanism imposes a reproducible stereochemical relationship between successive configurational units of the growing macromolecule. For substituted vinyl monomers, stereospecific insertion generates predominantly isotactic or syndiotactic sequences rather than the statistical stereochemistry of an atactic chain; for dienes, it may control cis/trans geometry or 1,2/1,4 microstructure ^[1]. Stereocontrol can arise from a chiral or site-symmetric catalyst, from the configuration of the chain end, or from cooperative site and chain-end effects. Tacticity is established by dyad, triad, or higher-sequence analysis, commonly using NMR spectroscopy ^[2]. The term describes a mechanistic mapping between monomer orientation and polymer configuration and is stronger than merely stereoselective polymerization, which may only enrich one microstructure. It is also distinct from polymerizing an enantiopure monomer without controlling newly created stereogenic centers; the polymerization step itself must govern the stereochemical sequence.