AUX or aux may refer to:
Auxins (plural of auxin /ˈɔːksᵻn/) are a class of plant hormones (or plant growth substances) with some morphogen-like characteristics.
An auxiliary power unit (APU) is a device on a vehicle that provides energy for functions other than propulsion.
Auxiliary police, also called Special Police, are usually the part-time reserves of a regular police force.
The Auxilia (Latin, lit. "auxiliaries") constituted the standing non-citizen corps of the Imperial Roman army during the Principate era (30 BC–284 AD), alongside the citizen legions.
Auxonne is a French commune in the Côte-d'Or department in the Burgundy region of eastern France. The inhabitants of the commune are known as Auxonnais or Auxonnaises.
An auxiliary verb (abbreviated aux) is a verb that adds functional or grammatical meaning to the clause in which it appears, such as to express tense, aspect, modality, voice, emphasis, etc.
An auxiliary force is an organized group supplementing but not directly incorporated in a regular military or police entity.
The Glider Pilot, Service Pilot, and Liaison Pilot badges were qualification badges of the United States Army Air Forces issued during the years of World War II by the AAF to identify a rating in one of three specialized, limited-duty pilot categories, whose required training differed from that of the traditionally trained, universally assignable military pilot.
Auxiliary Constables or Reserve Constables are unpaid citizens who volunteer their time and skills to a police force.