The five categories of hydraulic system applications are:
1. Industrial: Hydraulic systems are used in various industrial applications such as metal forming, material handling, and machine tools.
2. Mobile: Hydraulic systems are used in mobile applications such as construction equipment, agricultural machinery, and mining equipment.
3. Marine: Hydraulic systems are used in marine applications such as ships, boats, and offshore drilling rigs.
4. Aerospace: Hydraulic systems are used in aerospace applications such as aircraft landing gear, flight control systems, and hydraulic brakes.
5. Defense: Hydraulic systems are used in defense applications such as tanks, armored vehicles, and missile launchers.