This paper presents a formal means of classifying physical processes for virtual and physical kinetic art. From such a taxonomy may be derived a language for artistic expression. Additionally, the classification of physical processes facilitates the analysis of existing kinetic works based on their dynamic properties. This is to be preferred over a classification based on a kinetic work's static structural features, because these features do not necessarily reflect the piece's inherent dynamism. Finally, the characterization of physical processes is useful in the synthesis of virtual-kinetic art works, since it establishes a basis from which processes may be described algorithmically.