gradational vs graduated

gradational

adj
  • Of or pertaining to gradation. 

  • By regular steps or gradations. 

graduated

adj
  • Arranged by grade, level, degree. 

  • Having a university degree; having completed training. 

  • Increasing in rate with the taxable base. 

  • Of a tail, having successively longer feathers towards the middle. 

  • Marked with graduations. 

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