High Quality Content by WIKIPEDIA articles! Although the terms engineer and engineering date from the Middle Ages, they acquired their current meaning and usage only recently in the nineteenth century. Briefly, an engineer is one who uses the principles of engineering - namely acquiring and applying scientific, mathematical, economic, social, and practical knowledge - in order to design and build structures, machines, devices, systems, materials and processes. Some of the major branches of the engineering profession include civil engineering, military engineering, mechanical engineering, chemical engineering, electrical engineering, aerospace engineering, computer engineering, and biomedical engineering.