deteriorate

/dɪˈtɪriəˌreɪt/
verb
  1. To become worse in quality, condition, or value over time.
    • Her health started to deteriorate when she stopped exercising.
    • The old bridge began to deteriorate after years of neglect.
    • Relations between the two countries deteriorated after the trade dispute.
  2. To break down or decay physically.
    • If you don't seal the paint, the metal will deteriorate from rust.
    • The ancient manuscript had deteriorated into fragile, yellowed pages.
    • The wooden fence deteriorated quickly in the rainy climate.