Experimental tests of the strong interaction and its energy dependence in electron–positron annihilation

e+e− annihilation into quark–antiquark pairs is a valuable platform for the investigation of the strong interaction. The level of sophistication reached by theory and experiment allows one to verify predictions with significant precision for centre-of-mass energies ranging from the τ lepton mass up to about 200 GeV. This report summarizes studies of the dependence of the strong interaction on the energy scale. Determinations of αS from total cross-sections, hadronic branching fractions of the τ lepton and of heavy quarkonia, jet rates, and event shape observables confirm the energy dependence of the strong coupling constant. Tests of the flavour independence of the strong interaction and mass effects are reviewed. Perturbation calculations of mass effects allow the determination of the bottom quark mass at high energies and, therefore, the scale dependence of quark masses predicted by qcd. Experimental studies of theoretical approaches to hadronization are presented. Besides fragmentation functions, scaling violations, and longitudinal cross-sections, successes of the modified leading-logarithmic approximation and local parton–hadron duality are exemplified. Power suppressed corrections, which are expected to be related to hadronization, are discussed for mean values and distributions of event shape observables. From the energy dependence of the strong interaction missing higher-order terms of the perturbation series can be determined. The scrutiny of the scale dependence of αS showed no evidence for power corrections, light gluinos, or anomalous strong couplings. The results on αS from e+e− annihilation are also very consistent with determinations of the strong coupling constant from other hard processes.