Aeronautics (from Greek ὰήρ āēr which means "air" and ναυτική nautikē which means "navigation, Airmanship", i.e. "navigation of the air") is the science involved with the study, design, and manufacturing of airflight-capable machines, or the techniques of operating aircraft and rocketry within the atmosphere. While the term—literally meaning "sailing the air"—originally referred solely to the science of operating the aircraft,it has since been expanded to include technology, business and other aspects related to aircraft.
One of the significant parts in aeronautics is a branch of physical science called aerodynamics, which deals with the motion of air and the way that it interacts with objects in motion, such as an aircraft. The term "aviation" is sometimes used interchangeably with aeronautics, although "aeronautics" includes lighter-than-air craft such as airships, and includes ballistic vehicles while "aviation" does not.