loosely vs pro rata

loosely

adv
  • Approximately. 

  • Not tightly. 

  • Used to indicate an imprecise use of words; short for loosely speaking 

  • In a loose manner. 

pro rata

adv
  • In proportion to some factor that can be exactly calculated. 

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