lasting vs unstable

lasting

noun
  • A durable woollen material formerly used for women's shoes. 

  • The act or process of shaping footwear on a last. 

adj
  • Persisting for an extended period of time. 

unstable

adj
  • Readily decomposable. 

  • Not stable. 

  • Radioactive, especially with a short half-life. 

  • Unpredictable. 

  • Fickle. 

  • Having a strong tendency to change. 

  • Fluctuating; not constant. 

verb
  • To release (an animal) from a stable. 

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