This SAE Aerospace Recommended Practice (ARP) provides the technical terms and nomenclature@ together with their definitions and abbreviations/acronyms that are used in aerospace fluid power@ actuation and control systems. NOTE: ARP490 and ARP4493 are sources for definitions specifically for electrohydraulic servovalves. Field of Application The data contained herein applies to all types of aerospace vehicles and their fluid power@ actuation and control subsystems and components. Purpose The purpose of this document is to facilitate communications and to standardize the application of fluid power@ actuation and control system related terms in a consistent manner throughout the SAE publications and throughout the producer and user sectors of the aerospace industry.