Period after a full moon when the amount of the lighted side of the moon apperas to be decreasing?

The period after a full moon when the amount of the lighted side of the moon appears to be decreasing is known as the waning phase. During this time, the moon transitions from full to new, with the illuminated portion gradually shrinking each night. This phase includes the waning gibbous and waning crescent stages, marking a shift in the moon's visibility in the night sky.