This book presents a complete theory to explain the nature and behaviour of any technical system or artefact, including technical plants, equipment, machines, apparatus, mechanism, vehicles or parts. The task of this theory is to investigate and describe essential laws and phenomena, for example structure, functions, properties, origin, development in time and taxonomy. TTS describes a new (particularly for the English-speaking world) comprehensive and progressive approach to understanding technical systems, which contrasts with the previous loose synthesis of mechanisms, machine dynamics, mechanics of materials etc. The theory consists of more subtheories: transforming, process, development, evaluation and decision etc. Property theory occupies a central position, because the properties represent the main goal of designing technical systems. The unified modeling system is used for explaining and understanding the theory. The book is thorough and detailed and contains numerous charts, graphs, and tables. It can also be used as an aid-memoire or as a checklist for brainstorming. Many explanatory examples serve for understanding and motivation.