rotational vs rotatory

rotational

adj
  • Of, pertaining to or caused by rotation. 

noun
  • An employee in a job rotation scheme. 

  • Something, such as a joint, that moves by rotating. 

rotatory

adj
  • of, pertaining to, or causing rotation; rotational 

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