to become gradually damaged, worse, or less; to cause something to do this:
The old wooden house was slowly decaying.
Without proper maintenance, the old building began to decay, showing signs of wear and tear.
The neglected fruit started to decay, emitting a foul odor in the kitchen.
Environmental factors such as pollution can accelerate the decay of historical monuments.
Neglecting oral hygiene can lead to tooth decay and other dental problems over time.
