Aerodynamics, from Greek ἀήρ aero + δυναμική, is the study of motion of air, particularly as interaction with a solid object, such as an airplane wing. It is a sub-field of fluid dynamics and gas dynamics, and many aspects of aerodynamics theory are common to these fields. Aerodynamics is the study of how gases interact with moving bodies. Because the gas that we encounter most is air, aerodynamics is primarily concerned with the forces of drag and lift, which are caused by air passing over and around solid bodies. So for the modern world aerodynamics is a very important science. It is used to save fuel on anything that must move quickly through the air. It is used to make such vehicles stable. It also makes our streets safer around large skyscrapers. Aerodynamics is study of fluid motions over the objects paraticularly airfoil. Its objective can vary from harvesting energy from winds by aerodynamically designing blades of windmill, to obtaining greater and efficient lift by wings on airplanes.