What professional requirement distinguishes Astronaut/Cosmonaut from merely going to the edge of space?

Rigorous selection and training for orbital or deep-space missions

The established, high-formality titles like Astronaut and Cosmonaut imply a significant professional commitment beyond simply achieving space altitude. They are reserved for individuals who have successfully undergone rigorous selection processes and specialized training programs necessary for commanding, piloting, or serving as crew members on complex missions, particularly those involving sustained orbital mechanics or deep-space trajectories. The text stresses that this is not a casual label; the designation signifies a highly specialized individual whose skillset is matched to the demands of operational spaceflight, distinguishing them from non-certified space tourists or suborbital passengers.