flexion vs inflection

flexion

noun
  • Deviation from straightness. 

  • The act of bending a joint, especially a bone joint; the counteraction of extension. 

  • The state of being bent or flexed. 

inflection

noun
  • A turning away from a straight course. 

  • Change in the form of a word (morphologic change) to express different grammatical categories. 

  • Diffraction. 

  • Any form produced by such an instance of a change, such as the principal parts for any given stem: any of the declined or conjugated forms that constitute its declension or conjugation. 

  • An affix representing such an instance. 

  • A change in curvature from concave to convex or from convex to concave. 

  • A change in pitch or tone of voice. 

  • An instance of such change. 

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