verb (v)

• lengthen in time; cause to be or last longer(verb.change)

  Example:
  We prolonged our stay.
  

  Synonym:
  draw out, extend, protract
  

  source: wordnet30
• lengthen or extend in duration or space(verb.stative)

  Example:
  Prolong the treatment of the patient.
  

  Synonym:
  keep up, sustain
  

  source: wordnet30
• To extend in space or length; as, to prolong a line.(verb)

  source: webster1913