noun (n)

• free from obscurity and easy to understand; the comprehensibility of clear expression(noun.attribute)

  Synonym:
  clarity, clearness, limpidity, lucidness, pellucidity
  Antonym:
  unclearness
  

  source: wordnet30
• a lucid state of mind; not confused(noun.state)

  source: wordnet30
• The quality or state of being lucid.(noun)

  source: webster1913