English to English

verb (v)

• define clearly(verb.cognition)

  Example:
  I cannot narrow down the rules for this game.
  

  Synonym:
  nail down, narrow, peg down, pin down, specify
  

  source: wordnet30
• become more focus on an area of activity or field of study(verb.change)

  Synonym:
  narrow, specialise, specialize
  Antonym:
  branch out, broaden, diversify
  

  source: wordnet30