adverb (r)

• in place of, or as an alternative to(adv.all)

  Example:
  Felix became a herpetologist instead.
  

  Synonym:
  alternatively, or else
  

  source: wordnet30
• on the contrary(adv.all)

  Example:
  He didn't call; rather (or instead), he wrote her a letter.
  Used English terms instead of Latin ones.
  

  source: wordnet30
• In the place or room; -- usually followed by of.(adverb)

  source: webster1913