extra vs further

extra

adv
  • To an extraordinary degree. 

noun
  • A run scored without the ball having hit the striker's bat - a wide, bye, leg bye or no ball. 

  • A supernumerary or walk-on in a film or play. 

  • An extra edition of a newspaper, which is printed outside of the normal printing cycle, for example to report an important late-breaking event. 

  • The state or trait of being over the top, of behaving in an overly dramatic manner. 

  • Something additional, such as an item above and beyond the ordinary school curriculum, or added to the usual charge on a bill. 

  • Something of an extra quality or grade. 

adj
  • Beyond what is due, usual, expected, or necessary; extraneous; additional; supernumerary. 

  • Over the top; going beyond what is normal or appropriate, often in a dramatic manner. 

det
  • Denotes more. 

further

adv
  • To a greater extent or degree. 

  • Beyond what is already stated or is already the case. 

  • Also; in addition; furthermore; moreover. 

  • Following on (from). 

  • To, at or over a greater distance in space, time or other extent. 

verb
  • To help forward; to assist. 

  • To encourage growth; to support progress or growth of something; to promote. 

adj
  • More distant; relatively distant. 

  • More, additional. 

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