motivating vs motivative

motivating

adj

  • Effectively providing an incentive. 

motivative

adj

  • motivating; serving to motivate 

  • In, marked by or pertaining to the motivative case. 

noun

  • The motivative case, a case found in some languages (for example Basque) which marks the meaning "because of". 

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