decidable vs effective

decidable

adj
  • capable of being decided. 

  • in intuitionistic logic, a proposition P is decidable in a given theory if it can be proven from the theory that "either P or not P", i.e. in symbols: P∨¬P. 

  • describing a set for which there exists an algorithm that will determine whether any element is or is not within the set in a finite amount of time. 

effective

adj
  • Producing a decided or decisive effect. 

  • approximate; Not describing the fundamental dynamic changes in some system as they happen. 

  • Efficient, serviceable, or operative, available for useful work. 

  • Having no negative coefficients. 

  • Having the power to produce a required effect or effects. 

  • Actually in effect. 

noun
  • a soldier fit for duty 

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