The word aero is an adjective which means "of or for aircraft" or "pertaining to aeronautics". The word aero is also used as a free form to refer to aeronautic; aeronautical; aeronautics; aerospace etc. aeronautics is a science concerned with the study, manufacturing and design of flight capable machines. Aeronautics includes the techniques of operating these flight capable machines like aircrafts. The term aeronautics itself means "sailing in the air". We can say that aeronautics is the science of operating aircrafts and the word aero is only a free form of the word aeronautics or other such "aero" words mentioned above.