QUANTUM CHROMODYNAMICS

These lectures provide an overview of Quantum Chromodynamics (QCD), the $SU(3{)}_C$ gauge theory of the strong interactions. After briefly reviewing the empirical considerations which lead to the introduction of {\it colour}, the QCD Lagrangian is discussed. The running of the strong coupling and the associated property of {\it Asymptotic Freedom} are analyzed. Some selected experimental tests and the present knowledge of ${\alpha }_s$ are summarized. A short description of the QCD flavour symmetries and the {\it dynamical breaking of chiral symmetry} is also given.