operable vs operational

operable

adj
  • Able to be operated or used 

  • Able to be put into operation; practicable 

  • Able to be treated by surgery 

operational

adj
  • Effective or operative. 

  • Determined by means of practical measures. 

  • Of or relating to operations, especially military operations. 

  • Functioning and ready for use. 

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