What term is used for the moon that is decreasing in visibility?

The term used for the moon that is decreasing in visibility is "waning." This phase occurs after a full moon, as the illuminated portion of the moon gradually diminishes. During this period, the visible surface of the moon lessens from full brightness until it becomes a new moon. In contrast, when the moon is increasing in visibility from new to full, this is described as "waxing." The new moon phase marks the start of the lunar cycle with no visible illumination, while a full moon represents the peak, where the entire face of the moon is illuminated. Therefore, understanding these terms helps clarify the cyclical nature of the moon's phases and their visual appearance in the night sky.