What is defined as static stability?

The term static stability refers to a system's inherent ability to return to an equilibrium position after being disturbed. When an object, such as an aircraft, is displaced from its equilibrium position due to external forces or disturbances, static stability describes the tendency of that object to experience restoring forces that act to bring it back to its original position.

In the context of aviation, if an aircraft is subjected to a pitch change, for example, static stability would indicate how effectively the aircraft tends to return to its original attitude after the change. A statically stable aircraft will have a design that ensures that any minor deviations from its flight path will trigger aerodynamic forces that help it return to that path, thereby enhancing the safety and performance of the aircraft.

The other concepts are distinct: oscillation around a point pertains to dynamic stability, maintaining altitude is related to overall flight performance and control but does not specifically define static stability, and changing direction effectively involves maneuverability, which is not directly tied to the concept of static stability.