extra vs top-up

extra

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. 

adv
  • To an extraordinary degree. 

det
  • Denotes more. 

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. 

top-up

adj
  • That serves as an addition 

noun
  • The situation where a student who holds a qualification equivalent to part of a degree course is then accepted onto a degree course at an intermediate point, without having to start it from the beginning. 

  • Additional credit purchased for a mobile phone. 

  • An addition. 

  • An additional premium paid over the initial premium in order to increase benefit values. 

  • A serving of drink used to top up an existing glass. 

  • A dose of epidural anesthetic added to previously injected spinal anesthetic in combined spinal-epidural anesthesia 

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