fluidity vs instability

fluidity

noun
  • The quality of being fluid or free-flowing 

  • A measure of the extent to which something is fluid. The reciprocal of its viscosity. 

  • The state of being fluid rather than viscous 

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 fluidity and instability occurred in a corpus of books? (source: Google Ngram Viewer )