S: (v) devolve, deteriorate, drop, degenerate (grow worse) "Her condition deteriorated"; "Conditions in the slums degenerated"; "The discussion devolved into a shouting match"
W: (adj) degenerative [Related to: degenerate] ((of illness) marked by gradual deterioration of organs and cells along with loss of function) "degenerative diseases of old age"
W: (n) degeneration [Related to: degenerate] (the process of declining from a higher to a lower level of effective power or vitality or essential quality)