the world > relative properties > quantity > decrease or reduction in quantity, amount, or degree > [phrase] > falling off (2)
The waning, or gradual decrease of the visible illuminated area on the moon. Now rare except in phrases, on, uponthe wane, in (the, her, its) wane.
The process of declining or sinking to a weaker or inferior condition; gradual loss of force, vigour, vitality, or excellence of quality; falling…