"Gradual decay" refers to a slow and ongoing process of deterioration or decline over time. It implies that something is slowly falling apart or becoming weaker, usually due to age, neglect, or natural causes. Full definition
I have been divagating into Will Durant, not irrelevantly but mainly to go to the roots of our moral bankruptcy in defending human rights and averting the gradual decay of democracy. (religion-online.org)
I should note that entropy can also be defined as a gradual decay into disorder, but this definition is NOT the thermodynamic definition used in the Laws of Thermodynamics he was claiming was the base of his theory. (religion.blogs.cnn.com)
At the same time, Whitehead notes that «there has been a gradual decay of religious influence in European civilization. (religion-online.org)