noun (n)

• powerful and effective language(noun.communication)

  Example:
  His eloquence attracted a large congregation.
  

  Synonym:
  fluency, smoothness
  

  source: wordnet30
• Fluent, forcible, elegant, and persuasive speech in public; the power of expressing strong emotions in striking and appropriate language either spoken or written, thereby producing conviction or persuasion.(noun)

  source: webster1913