What Is Engineering? Engineering is an art of applying science to the optimum conversion of the resources of nature to the uses of humankind. It is based principally on physics, chemistry, and mathematics and their extensions into materials science, solid and fluid mechanics, thermodynamics, transfer and rate processes, and systems analysis. It is thus we must define Engineering: "the practical application of science and math to commerce or industry". In other words "the art or science of applying scientific knowledge to practical problems".