that is vs very well

that is

adv
  • In other words; that is to say. Used to introduce a clarification or explanation 

very well

adv
  • Used other than figuratively or idiomatically: see very, well. 

  • Used to weaken the effect of certain modal verbs. 

intj
  • A standard response by a superior to a report or confirmation. 

  • Indicating acceptance, often with resignation or acquiescence, of a statement or situation. 

adj
  • Used other than figuratively or idiomatically: see very, well. 

How often have the words that is and very well occurred in a corpus of books? (source: Google Ngram Viewer )