central vs operant

central

adj
  • Exerting its action towards the peripheral organs. 

  • Having or containing the centre of something. 

  • Being in the centre. 

  • Being very important, or key to something. 

noun
  • centre 

operant

adj
  • That operates to produce an effect. 

noun
  • Any of a class of behaviors that produce consequences by operating (i.e., acting) upon the environment. 

  • An operative person or thing. 

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