What indicates that altitude hold mode is engaged in the cockpit?

The presence of 'ALT HOLD' displayed on the pitch Flight Mode Annunciator (FMA) indicates that altitude hold mode is actively engaged in the cockpit. This specific designation is crucial because it visibly confirms to the pilot that the aircraft is maintaining a set altitude, which is a critical aspect of automated flight operation. The FMA is designed to provide clear, immediate feedback about the flight control system's status and configurations. When 'ALT HOLD' is shown, it reassures the pilot that the autopilot system is functioning correctly and will maintain the selected altitude, allowing the pilot to proactively manage other aspects of the flight without needing to consistently monitor altitude manually.