Visibility is defined as the greatest distance at which:

Visibility is defined as the greatest distance at which selected objects can be seen and identified. This definition is crucial for aviation and meteorological observations, as it directly impacts flight safety and operations.

In practical terms, "selected objects" refers to distinct landmarks or targets that pilots or observers can use as references, such as runway lights, buildings, or other specific markers. The ability to identify these objects is what distinguishes visibility in this context; it is not just about seeing any object, but being able to correctly identify specific ones that are important for navigation and safety.

Understanding this definition helps in interpreting weather reports and making informed decisions regarding flight operations, as varying visibility conditions can significantly affect the ability of pilots to operate aircraft safely.