Solution polymerization is a polymerization process whose initial reaction mixture contains monomer dissolved in a molecular solvent together with an initiator or catalyst as required. In the strict homogeneous case, both monomer and growing polymer remain soluble under the reaction conditions, so propagation occurs throughout a single liquid phase ^[1]. The solvent dilutes the reacting species, moderates viscosity, and transfers heat, but it can also alter catalyst speciation, propagation kinetics, and molar mass through chain transfer; solvent-derived chain transfer is a defining kinetic consideration in radical solution polymerization ^[2]. If the forming polymer becomes insoluble and precipitates, the process is classified as precipitation polymerization rather than homogeneous solution polymerization. The method is also distinct from suspension and emulsion polymerization, where monomer-rich droplets or particles are dispersed in a continuous phase. Removal or retention of solvent after conversion does not define the polymerization; classification depends on the physical state and composition of the reaction medium during chain growth.