Other forms: deteriorated; deteriorating; deteriorates
When something gets worse due to neglect or an unfortunate health problem, stuff starts to deteriorate — or fall apart.
The word deteriorate describes anytime something gets worse. Due to neglect, a relationship can deteriorate but so can the American highway system. Sadly, there seems to be no end to applications for the word deteriorate. And, the truth is at a certain age we all start deteriorating too.