Engineering is the professional art of applying science to the optimum conversion of the resources of nature to the uses of humankinD、Engineering has been defined as the creative application of "scientific principles to design or develop structures, machines, apparatus, or manufacturing processes, or works utilizing them singly or in combination." The term engineering is sometimes more loosely defined, especially in GreatBritain, as the manufacture or assembly of engines, machine tools, and machine parts.Associated with engineering is a great body of special knowledge; preparation for professional practice involves extensive training in the application of that knowledge. The function of the scientist is to know, while that of the engineer is to do. The scientist adds to the store of verified, systematized knowledge of the physical world; the engineer brings this knowledge to bear on practical problems.Engineering is based principally on physics, chemistry, and mathematics and their extensions into materials science, solid and fluid mechanics, thermodynamics, and systems analysis.