adherence vs instability

adherence

noun
  • An extent to which a patient continues an agreed treatment plan. 

  • The fulfilment of the legal obligation of residing with wife or husband. 

  • Faithful support for some cause. 

  • A close physical union of two objects. 

instability

noun
  • The quality of being unstable. 

  • A state that is not in equilibrium, or in which a small change has a large irreversible effect. 

How often have the words adherence and instability occurred in a corpus of books? (source: Google Ngram Viewer )