noun (n)

• powerful and effective language(noun.communication)

  Example:
  Fluency in spoken and written English is essential.
  

  Synonym:
  eloquence, smoothness
  

  source: wordnet30
• skillfulness in speaking or writing(noun.cognition)

  Antonym:
  disfluency
  

  source: wordnet30
• the quality of being facile in speech and writing(noun.attribute)

  Synonym:
  articulateness, volubility
  

  source: wordnet30
• The quality of being fluent; smoothness; readiness of utterance; volubility.(noun)

  source: webster1913