Definition of decays:
(n) :
(ecology, medicine) The process or result of being gradually decomposed; rot, decomposition.
(n) :
A deterioration of condition; loss of status, quality, strength, or fortune.
(v) :
(intransitive) To deteriorate, to get worse, to lose strength or health, to decline in quality.
(v) :
(intransitive, of organic material) To rot, to go bad.
(v) :
(intransitive, transitive, physics, chemistry, of an unstable atom) To change by undergoing fission, by emitting radiation, or by capturing or losing one or more electrons; to undergo radioactive decay.
(n) :
a gradual decrease of a stored charge, magnetic flux, current, etc.